Shown is the state flag of Delaware, part of a pane of stamps showing the flags of each of the 50 states.

Although the Delaware State Flag was not adopted until 1913, the story behind its design began in the colonial era. When Delaware became an independent state in 1776 there was an immediate need to produce what is known as a Great Seal for the State. A Seal is an impression or mark that appears on official documents of the State and is an important means of identifying and authenticating government papers.

On January 17, 1777, a committee appointed to design a Great Seal by the Delaware General Assembly presented their report to the Assembly. In this report the Committee described the new design of the Seal. (See transcription) In addition, it was decided that New Castle County's Seal would serve as the State Seal until the new one was made. In 1847, the new state motto, "Liberty and Independence" was added to the Seal.

When a committee was appointed in 1913 to design the official flag of the State, the members chose the Seal's center section (called the Coat of Arms) as the focal point of the flag. The diamond shape that surrounds the Coat of Arms is derived from Delaware's nickname - the Diamond State. This name has traditionally been attributed to Thomas Jefferson. The date, December 7, 1787, reflects the pride in being the first state to ratify the United States Constitution. The flag's main colors, colonial blue and buff, were chosen to honor General George Washington. The hero of the American Revolution wore a uniform composed of these colors.