U.S. state flag consisting of a green field (background) with the state seal in the centre.

The 19th-century territorial seal of Washington had a detailed naturalistic scene with sea and mountains and a woman in the foreground epitomizing hope, surrounded by a log cabin, wagon, and fir forest. That design was replaced at the time of statehood in 1889. Charles Talcott, a jeweler who had been called upon to engrave the seal, recommended a simple and striking design with the name of the state, the date of its admission to the Union, and a bust of George Washington (Washington, George). That seal was adopted on July 4, 1889. In 1915 Mrs. Stephen J. Chadwick, a member of the Daughters of the American Revolution, chose a background of green for the flag of the “Evergreen State” and placed a bust of President George Washington in the centre. In 1920 the training ship owned by the Washington State Nautical School flew a similar flag.

The green state flag adopted by the state legislature in 1923 featured the state seal in its centre. Originally the flag was to be decorated with green fringe, but after 1925 it was designated as having a fringe of gold when displayed on certain occasions. A more precise artistic definition was given to the flag on April 19, 1967. That law requires the seal to appear correctly on both sides of the flag, although in practice most flags are still made single-sided. Washington is alone in having a U.S. state flag with a green background.