Kent County was originally chartered by the Duke of York on June 21, 1680, as St. Jones County - carved out of New Amstel and Hoarkill counties. The St. Jones River, which runs through Dover, gave the original name. On August 24, 1682, the Duke transferred the county to William Penn, who renamed it Kent after his ancestral county in England. The English began settling the St. Jones River valley around 1670, when it was still known as Wolf Creek. Penn ordered a court town to be laid out and the courthouse was built in 1697. The town of Dover - named after the English Dover in Kent - was formally laid out in 1717. Delaware became the capital in 1777 and the First State on December 7, 1787, when it became the first to ratify the U.S. Constitution. Kent County was subdivided, like all Delaware counties, into Hundreds - colonial subdivisions of administration, militia, and taxation. The original six Hundreds were Duck Creek, Little Creek, Dover, Murderkill, Milford, and Mispillion. Murderkill, despite the name, refers not to a violent event but to a Dutch translation: the Lenape called the river Moeder-Kill, or Mother River; Dutch settlers heard it as Mörd-Kil, which became Murder Kill in English. The misunderstanding stuck.

Kent County's economy in the eighteenth and early nineteenth centuries was based on small grain farms - wheat, corn, oats. The agriculture was less labor-intensive than the tobacco plantations of southern Delaware and Maryland's Eastern Shore. Kent County farmers needed fewer enslaved workers, and as a result the county had a higher proportion of free Black residents than the slave-economy counties to the south. By the early 1800s, the free Black community in Kent County included multi-generation families who had been free since before the Revolution. Methodist and Quaker influence reinforced manumission. By 1860, the vast majority of African Americans in Kent County were free; only a few hundred were still enslaved. The free Black community established its own churches, schools, and burial grounds. The Star Hill A.M.E. Church, founded near Dover by formerly enslaved members of the African Methodist Episcopal denomination, dates from this era. The Big Quarterly festival - a religious and cultural gathering organized by Peter Spencer in 1814 that has been held every August for over two centuries - is the oldest continuous African American religious gathering in America.

The A7L spacesuit ILC Dover built for Apollo had to accomplish what no other garment in human history had attempted - keeping a human alive on the surface of the Moon. The suit had to provide pressure, oxygen, thermal protection, micrometeorite defense, and full body mobility, all while being light enough to walk in under one-sixth Earth gravity. The seamstresses who built the suit worked under extraordinary precision standards. Sewing tolerances were measured in fractions of a sixteenth of an inch. The Spacesuit Production team included Hazel Fellows, who designed many of the layered constructions, and Eleanor Foraker, who supervised the seamstress group. Their names are not in Apollo's official history with the prominence of the astronauts or the engineers, but the suits would not have existed without them. ILC Dover's space-suit business continued through Skylab, the Space Shuttle, and the ISS. The company still designs and manufactures all U.S. EVA suit assemblies, including the latest xEMU and Axiom suits for Artemis lunar missions. Frederica is a small farming town in Kent County. It also helped make the Moon habitable for two days.

Bombay Hook National Wildlife Refuge covers 16,000 acres of tidal marsh, freshwater impoundments, and upland forest along the Delaware Bay in northeastern Kent County. The refuge was established in 1937 to protect waterfowl habitat on the Atlantic Flyway. Every fall, tens of thousands of snow geese descend on the refuge from their Arctic breeding grounds, creating one of the largest snow goose concentrations on the East Coast. The flocks can darken the sky when they take wing. Tundra swans, mallards, pintails, green-winged teal, and northern shovelers join them. The refuge holds a twelve-mile auto tour route through the marsh, with five observation towers along the way. Bombay Hook is named for the Dutch hoek - a hook of land - and the bombay, a corruption of the Lenape word for the area. The refuge sits at one of the most important migratory bird stopovers in the eastern United States. On a cold November morning, the cacophony of waterfowl makes conversation impossible. The geese have been coming to this marsh for thousands of years before the refuge existed. The refuge ensures they still have somewhere to come back to.

Kent County is Delaware's least populous county - 181,851 residents in the 2020 census - but it is the most populous county in the United States to hold that distinction within its state. Dover, the county seat and the state capital, contains the Delaware Legislative Hall, the Delaware State Capitol Complex, and the offices of most of the state's executive branch. The Kent County Levy Court, the unusually-named county legislative body, dates back to the colonial era when local government taxes were called levies. Bombay Hook, Dover Air Force Base, Delaware State University, ILC Dover, Dover Motor Speedway, the Delaware State Fair in Harrington, and the Amish community west of Dover all sit within the county. The county runs from the Mason-Dixon Line at its southern boundary to the New Castle County line at its north - about 30 miles. The Delaware River, the Delaware Bay, and the inland farming districts give the county three different landscapes within a hour's drive. The First State's middle county quietly holds the state government, the moon-suit factory, and the bird refuge. Most Delawareans pass through it without realizing how much it contains.