Dover was founded as the court town for newly established Kent County in 1683 by William Penn. A man of deep religious convictions, Penn wrote numerous works in which he exhorted believers to adhere to the spirit of Primitive Christianity. He was imprisoned several times in the Tower of London due to his faith, and his book No Cross, No Crown (1669), which he wrote while in prison, has become a Christian classic of theological literature.

It was named by William Penn for a town and major ferry port in Kent, England (for which, incidentally, Kent County is named).

The city is laid out around The Green, a tree-shaded square surrounded by colonial buildings. It was the location of many rallies, troop reviews, and other patriotic events, and to this day, The Green remains the heart of Dover's historic district and is the location of the Delaware Supreme Court and the Kent County Courthouse.

The capital of the state of Delaware was moved to Dover from New Castle in 1777 because of its central location and relative safety from British raiders on the Delaware River.

Dover was the home of Caesar Rodney, the popular wartime leader of Delaware during the American Revolution and signer of the Declaration of Independence. He is buried in an unmarked grave in his family's plot on their 800-acre farm east of Dover Air Force Base. A cenotaph in his honor is erected in the cemetery of the Christ Episcopal Church near The Green.

The Kraft Foods plant in Dover has been the plant that manufactures Jell-O since 1964 when it relocated from Bloomfield, New York.

Woodburn Mansion is not only home to Delaware governors, but reportedly to several spirits as well, including one who occasionally floats around dressed in a Revolutionary War costume. According to staff, the ghosts who reside at Woodburn have long had a love of good wine and sometimes help themselves to the vintage wines in the cellar.

Dover International Speedway was nicknamed The Monster Mile by track CEO Denis McGlynn in the mid-1970s, largely because of how demanding it was on drivers and equipment. From 2007 through 2009 the speedway received an upgrade that expanded the track's facilities, and a 46-foot fiberglass creature named Miles the Monster was built outside the racetrack.

Firefly Music Festival has been held in the Woodlands of Dover International Speedway every summer since 2012. In past years, the festival has included up to seven stages and more than 100 performances.

Dover was recognized by Guinness World Records when 396 attendees at the Firefly Music Festival lathered up to shower together for at least 5 minutes, the most ever to shower simultaneously at a single venue. The feat was sponsored by soap-maker Irish Spring and was accomplished on June 15, 2018.