Illinois Statehood: December 3, 1818, and Its Flag

Illinois became the 21st state on December 3, 1818. President James Monroe signed the resolution admitting Illinois to the Union after delegates had written a state constitution at Kaskaskia. The state flag arrived almost a century later: Illinois adopted its first official flag in 1915.

Illinois state flag with an eagle, state emblem and Illinois lettering on a white field.
FORTISVEX catalog illustration of the modern Illinois state flag. The flag design is separate from the statehood date.

When is Illinois's state birthday?

December 3 is Illinois's statehood anniversary. The Illinois Statehood Day statute commemorates December 3, 1818, as the date Illinois became the 21st state. This was an admission to the Union, not an original-state ratification of the U.S. Constitution.

How did Illinois become a state?

The path ran through Kaskaskia, then the territorial capital. An enabling act approved on April 18, 1818, set the conditions for statehood. Delegates assembled in August and adopted Illinois's first constitution on August 26. The Illinois State Archives' constitution exhibit explains that the document was not submitted to a popular ratification vote.

Admission was not automatic. The Archives records objections in Congress from members who thought the constitution did too little to prohibit slavery. Congress nevertheless approved admission, and Monroe signed the resolution on December 3. Remembering that debate gives the anniversary more context than a date alone.

Which dates matter in Illinois statehood and flag history?

  • 1818: Illinois became a state.
  • 1915: Illinois adopted its first official state flag.
  • 1969: A change authorized adding the state's name to the flag.
  • 1970: The standardized flag with the name became official.

How the Illinois state flag developed

A design competition organized through the Daughters of the American Revolution led to Lucy Derwent's winning entry. The 1915 flag law made the emblem of the Great Seal the basis of the flag. Because the early law lacked detailed specifications, reproductions varied.

Later, service member Bruce McDaniel urged that the state name be added so the flag would be easier to identify. The Illinois Department of Natural Resources' flag history describes the resulting 1969 authorization and the standardized design that became official on July 1, 1970.

Was today's Illinois flag flown at statehood?

No. The official flag tradition began in 1915, long after admission in 1818. For a birthday exhibit, place a modern flag beside the statehood date and label the two milestones clearly rather than presenting the flag as an 1818 artifact.

Explore Illinois flags and other state birthdays

For a statehood display, compare the sizes, materials and mounting options in our Illinois state flag collection. For more anniversary dates, visit the U.S. state birthday calendar.

Sources and further reading

Oct 24th 2026 Sabrina C.

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