From the first inhabitants of this land, the Lenape/Nanticoke tribes, to Dutch settlers in the early 17th century to the present day, Sussex County has seen many visitors. Some of those visitors have stayed, farming the land, harvesting resources, working and calling this new land home. The largest, but historically least populous, county in the state of Delaware, most of the County’s economy revolves around agriculture, as Sussex produces the most poultry of any county in the United States, but tourism plays a large role in the economy, especially at the County beaches.  Sussex County has had its share in the limelight of history. Below are some key dates in Sussex County and Delaware's history:

• Archaeologists estimate that the first inhabitants of Sussex County, the southernmost county in Delaware, arrived between 10,000 and 14,000 years ago. Tribes eventually were pushed west toward modern day Oak Orchard. Today the Nanticoke Tribe numbers near 4,000 members.  They host their annual Pow-Wow the second week of September, with attendees numbering near 15,000. 
• 1609 – Henry Hudson and his crew aboard the Half Moon enter the mouth of what will become known as Delaware Bay.
• 1613 - Cornelius Jacobsen Mey, a Dutch navigator, discovered and named both Cape May and Cape Henlopen (originally Hindlopen) in the Delaware Bay.
• 1631 – Dutch established a trading post in what is present-day Lewes, calling the colony Zwaanendael, or "Valley of the Swans".
• 1664 - The English wrested control of New Netherland from the Dutch. The Dutch briefly recaptured the territory in 1673 as part of the Third Anglo-Dutch War. At that point, they established courts in the town of New Castle and at the Hoerkill at the southern end of the territory, effectively creating two counties out of the territory. After the war concluded in 1674, the Delaware territory was returned to the English. It was then placed under the control of James Stuart, Duke of York.
• 1681-1682 – The King of England grants Pennsylvania and Delaware to William Penn, an English proprietor who names Delaware's southernmost county for his home county of Sussex in England. The land grant sets off years of disputes with the Calvert family of neighboring Maryland, who challenge the boundaries between Delaware and Maryland.
• 1704 – Delaware, also known as the "Three Lower Colonies," is established as its own government independent of Pennsylvania, though still under English rule.
• 1707 – 3,000-acre Broad Creek Reservation formed around what is today modern-day Laurel. Reservation was sold in 1768, and the Tribe migrated east to modern day Oak Orchard.
• 1711 – Native American reservation near Millsboro began. Last tract sold to William Burton in 1731.
• 1732 - Charles Calvert signed a territorial agreement with William Penn's sons that drew a line somewhere in between the two colonies and renounced Calvert's claim to Delaware. But Lord Baltimore later claimed that the document he signed did not contain the terms he had agreed to and refused to put the agreement into effect. Beginning in the mid-1730s, violence erupted between settlers claiming various loyalties to Maryland and Pennsylvania. The border conflict between Pennsylvania and Maryland would be known as Cresap's War.
• 1750-51 - A team of surveyors from both colonies surveyed and marked the Transpeninsular Line, which established the southern boundary of Sussex County. However, residents of the disputed territory continued to pay taxes to Maryland into the 1770s.
• 1763 – Deep Creek Iron forge established outside Georgetown; iron working industry begins in Sussex County.
• 1763 - 1767 - Charles Mason and Jeremiah Dixon surveyed the Mason-Dixon line, settling Sussex County's western borders. After Pennsylvania abolished slavery in 1781, the western part of this line and the Ohio River became a border between free and slave states; the survey formalizes the boundary, and thus brings an end to decades of dispute that began with the Penn’s and Calvert’s.
• 1776 to 1783 – Revolutionary War. It has been variously estimated that anywhere from half to four-fifths of the 14,000 Sussex Countians in 1776 were loyalists to King George. There were several assemblymen and respected politicians here in Sussex County that by 1774, had been forced to flee to Canada, with their property confiscated and their lives in ruins.
• 1787 – Delaware becomes the first state to ratify the U.S. Constitution.
• 1791 – Georgetown platted out and established as the new County seat; the County seat had been located at Lewes but was relocated to a more central portion of the County.
• 1791 First Return Day held.  - The Delaware Legislature required all votes to be cast on Election Day at the new County Seat in Georgetown, Delaware. Thus, all Sussex County residents had to travel to Georgetown in order to vote on Election Day, and then return two days later to hear the results – hence the name Return Day. The winners of that year’s political races would parade around the town circle in horse pulled carriages, and then the losers and the chairs of the county’s political parties would perform the ceremonially “bury the hatchet” into a tub of sand. In 1811, voting districts were created across the state, but the Board of Canvassers would still meet two days later in Georgetown to announce the final election results.
• 1813 – Lewes bombarded by the British during the War of 1812.
• 1830s to 1840s – Canning industry begins.
• 1856 - Harriet Tubman organized what is considered by Tubman scholars to be “one of her most complicated and clever escape attempts.”  Tubman located a slave named Tilly in Baltimore. Tubman decided she and Tilly would travel by steamboat to Seaford, first sailing south down the Chesapeake Bay then up the Nanticoke River. Tubman and Tilly spent the night at a hotel located atop the hill. Nearly arrested by slave traders the following morning, accounts note that the hotel landlord intervened on behalf of the two women. Thanks to Tubman’s letter of passage which identified her as a free African American woman from Philadelphia, she and Tilly obtained passes to safely travel north, first by train to Camden, then by carriage to Wilmington.
• 1859 – Railroad reaches Delmar. Farmers are now able to ship perishable goods outside of Delaware to cities such as Wilmington, Philadelphia and Baltimore.
• 1860 to 1865 – The Civil War period sees Delaware become a border state, siding with the Union. But Confederate sympathies run deep in southernmost Sussex County.
• 1871 – Strawberries first planted near Selbyville.
• 1872 – Rehoboth Beach founded as a tent revival meeting grounds.
• 1878 – Rail line reaches Rehoboth Beach; popularity of beaches spreads south.
• 1903 – Sussex County Levy Court is abolished by Delaware General Assembly and reformed as a 10-member panel.
• 1915 – The Delaware General Assembly again abolishes and reforms the Levy Court, this time as a three-member board of commissioners; the new Levy Court takes effect in 1917.
• 1919 – Last ship built in Bethel, which had been a popular ship-building port along Broad Creek, a tributary of the Nanticoke River and Chesapeake Bay.
• 1923 – Cecile Steele of Ocean View orders 50 chicks for her egg-laying business, but instead receives 500 birds thanks to a clerical error. The foul-up gives birth to the modern broiler industry, and will make Sussex County not only the birthplace, but the leading county of broiler production in the United States.
• 1924 – du Pont Highway opens, connecting Sussex County to points northward.
• 1939 – The DuPont Company opens the first plant to commercially produce nylon in Seaford on December 15, making Seaford the Nylon Capital of the World. 
• 1943 – Levy Court of Sussex County purchases ground near Georgetown for airport. U.S. Navy, and later a private firm, All American Engineering, use the property for training and testing grounds.
• 1967 – Delaware Technical Community College opens in Georgetown in September.
• 1970 – Sussex County, by authority of the Delaware General Assembly, shifts from Levy Court system to County Council form of government. Two Council seats are to be added to the new County Council, beginning with the legislation's effective date of Jan. 1, 1971. That act brought to five the total number of elected members on the panel.
• 1974 – Sussex County Council adopts first official County flag, a design based on merged imagery: the Dutch flag and the sheaf of wheat from William Penn’s County seal. The flag was designed by William C. Scott of Selbyville.
• 1985 – Population of Sussex County reaches 100,000.
• 1995 – Dogfish Head Brewery opens in Milton. 
• 1996 – County offices relocate from the Sussex County Courthouse on The Circle in Georgetown to the current County Administrative Offices building next door.
• 1998 – The Delaware Center for the Inland Bays begins partnership with Sussex County to manage the 150-acre James Farm as a nature preserve at Holts Landing. 
• 2001 – The Sussex County Land Trust was formed to help protect open space. The SCLT is a nonprofit conservation organization, dedicated to protecting natural, cultural, and agricultural resources. Since its creation the group has preserved well over 2,000 acres in Sussex County. 
• 2004 – Little League Softball World Series moves to Sussex County.
• 2006 – Reader’s Digest names Rehoboth Beach Boardwalk among ‘Best of America” and profiles iconic resort attraction in May edition.
• 2006 – Robert Stickels, the longest serving County Administrator under the County Council form of government, retires. David B. Baker appointed as County Administrator.
• 2007 – The prototype of the first-ever County flag, designed by William C. Scott of Selbyville in 1974, is generously donated to the County by Mr. Scott in December 2007. The flag remains on display in the County Administrative Offices building in Georgetown.
• 2008 – Delaware’s senior U.S. senator, Joseph R. Biden III, elected as Vice President of the United States; visits Georgetown for Return Day to celebrate win during post-election tradition.
• 2008 – A new $13 million state-of-the-art Emergency Operations Center opens next to the Sussex County Airport outside Georgetown, giving the County a modern facility to process 911 calls and coordinate responses to emergency events.
• 2009 – A new 3,109-foot runway opens at the Sussex County Airport near Georgetown, giving pilots an alternate runway to use when landing smaller aircraft in crosswind conditions. The runway is the second at the airport, joining the main 5,000-foot runway.
• 2010 – Population of Sussex County reaches 200,000.
• 2011 – David B. Baker in January announces planned retirement from County government after 33 years of service, five of those as County Administrator; Georgetown-area native Todd F. Lawson named as successor in July. Baker retires Dec. 31, 2011.
• 2011 – Todd Lawson becomes Sussex County Administrator on July 29, 2012.
• 2011 – National Resources Defense Council awards five-star ratings to Rehoboth Beach and Dewey Beach for water quality.
• 2011 – Extreme Home Makeover: Home Edition television crews come to Delaware to film construction of weeklong project to erect new facility for Jusst Soup ministry near Milton.
• 2011 – Earthquake registering 5.8 on the Richter scale emanates in central Virginia, rattling many locales across the mid-Atlantic and East Coast, including Sussex County and Delaware.
• 2012 – Charles W. Cullen Bridge, known locally as the Indian River Inlet Bridge, opens with the fifth span since original crossing in 1934, this one a cable-stayed bridge that becomes an eye-catching beacon in the coastal landscape.
• 2014 – Sussex County builds and operates its first park, a twenty-acre parcel just outside Woodland.
• 2014 – Social justice advocate and attorney Bryan Stevenson, originally from Milton, publishes memoir Just Mercy: A Story of Justice and Redemption, which goes on to critical acclaim as both a New York Times bestseller and eventual big-screen adaptation (2019).
• 2016 – Lawrence Lank retires as Director of Sussex County Planning and Zoning after 47 years of service. After starting with the County in 1969, he drew the first Sussex County zoning map in 1971.
• 2017 – Then Former-Vice President Joe Biden and wife Jill, purchase home in the North Shores community near Rehoboth Beach.
• 2018 – Sussex County Councilman George Cole retires after 32 years. The longest serving Councilperson, a member of the Cole family has held that council seat since its creation. His father Charlie held the office until his death in 1985, and his mother Kitty until George was elected.  
• 2019 – Dogfish Head Brewery is acquired by the Boston Beer Company for $300 Million.
• 2020 – Sussex County population reaches 235,000, a 20% increase from 2010. 
• 2020 – Delaware’s own Joseph R. Biden is elected the 46^th President of the United States. This brings attention to Sussex County as he has a home near Cape Henlopen. 
• 2021 – Milton native Jimmie Allen named New Male Artist of the Year during the Academy of Country Music Awards, the first Black solo performer to win the honor.