John Messinger (January 4, 1771 – September 16, 1846) was an American pioneer, politician, teacher, and surveyor who was the first Speaker of the Illinois House of Representatives. Born in Massachusetts, Messinger was educated in Vermont and married the daughter of Matthew Lyon. He left with Lyon to Kentucky, but disagreed with his stance on slavery and came to the Indiana Territory in 1802. He served in the Indiana Territorial Legislature and advocated for the creation of the Illinois Territory. When the state of Illinois was created in 1818, he co-authored its constitution and served in its first General Assembly as Speaker of the House. Messinger was also a prominent surveyor, establishing what is now the state line between Illinois and Wisconsin on behalf of the U.S. government.[1]