The 1918 Illinois Statehood Centennial half dollar (often referred to as the "Lincoln" half dollar) has the distinction of being the first US commemorative coin issued to celebrate the history of an individual state. Each of the previous commemorative coins - with one exception - was issued in conjunction with a World's Fair or Exposition.


"What's the exception?" I hear you ask. Answer: the 1917 William McKinley gold dollar which supported the building of a McKinley memorial in Niles, Ohio. The McKinley coin was approved and issued ahead of the Illinois half dollar, and it was most definitely associated with a specific state (Ohio) vs. being connected to an exposition. So, why isn't it considered the first "state commemorative?"
Simple, while it supported a state-specific memorial, the coin was not issued to commemorate the history of Ohio as a state, it was issued to specifically support the McKinley Memorial in Niles (McKinley's birthplace) and to celebrate his life and accomplishments. McKinley was the 25th president of the United States (a national figure).
(Note: The McKinley Memorial in Niles, Ohio should not be confused with the McKinley Monument constructed in Canton, Ohio - they are two distinct places and are managed by different groups.)(Additional Note: McKinley was assassinated in September 1901 while attending the Pan-American Exposition that was being staged in Buffalo, NY. He was the third (of four) US presidents to be assassinated.)In the years immediately following the Illinois Statehood Centennial coin's approval, commemorative half dollars were authorized for several statehood centennial anniversaries: 1920 Maine, 1921 Alabama and 1921 Missouri. In later years, the 1925 California (75th), 1935-39 Arkansas (100th), 1936 Arkansas-Robinson (100th) and 1946 Iowa (100th) coins were all approved to mark statehood milestones.
A number of other coins that collectors have assigned a state's name to (for quick and easy reference) are sometimes mistakenly thought to be statehood anniversary commemoratives, but are, in fact, celebrating very different milestones:
Colonial Anniversaries: 1935 Connecticut, 1936 Delaware and 1934 Maryland
Pre-Statehood Independence Anniversaries: 1925 Vermont-Battle of Bennington and 1934-38 Texas
Discovery Anniversaries: 1928 Hawaiian
Territorial Anniversaries: 1936 Wisconsin
Of course, there have also been a number of cities and counties that have celebrated their histories with a US commemorative coin (e.g., Providence, Rhode Island; York County, Maine), but they're a subject for a future post!