Evolution of County Organization By Howard F. Dyson, 1918
Pike county was the first to be organized in the Military Tract. It was set apart from Madison county in 1821, and at that time embraced the whole of the country north and west of the Illinois river, including what is now the counties of Cook and Will.
In January, 1825, ten new counties were created from the Military Tract. This county was named in honor of Gen. Phillip Schuyler, who was a soldier of the Revolutionary war, also served as a member of congress from New York during a part of the war period, and was later a United States senator from the same state.
Of the 10 counties created from the Military Tract in 1825, Adams, Peoria, and Schuyler were the only ones that had the required population necessary for immediate organization.
As originally organized, Schuyler county was 30 miles north and south by 36 miles east and west, including all of Brown county. In 1839, Brown county was set off and Crooked creek was made the boundary line from the Illinois river to the northeast corner of township one north, range two west, where the dividing line between the two counties ran west on the township line, thus leaving the county six townships east and west and three and a fraction north and south.
The civil boundary of the county was even more extended under the legislative enactment as Schuyler was given civil jurisdiction over that part of the Military Tract which now includes the counties of McDonough, Warren, Henderson, Mercer, and a portion of Rock Island county. From court records it appears that McDonough was the only one of the five counties that shared the civil government of Schuyler.