The fortunes of Rock Island County have been those of the State of Illinois. In 1541, Ferdinand De Soto discovered the Mississippi River, crossing it somewhere near Memphis; and upon this discovery rested Spain’s claim and title to the “far west.” The country now known as the State of Illinois is shown on the very early Spanish maps as a part of Florida. Spain made no attempt., however, to plant her settlements in the “Illinois.” In 1763, at the close of the French and Indian Wars, Illinois became British territory, and so remained until July 4, 1778, when Colonel George Rogers Clark and his Virginians captured the British forts and settlements. In October of that year, Illinois was by act of the General Assembly of Virginia created the “County of Illinois,” and became a part of the commonwealth of Virginia. During the Revolutionary War, Illinois and what is now the states of Ohio, Indiana, Michigan and Wisconsin, was claimed by each of the states of New York, Massachusetts, Connecticut and Virginia. In 1785 these states surrendered their claim to the General Government, and then Congress passed an act for the government of this country, which was designated “Western Territory.” but nothing was done towards organizing a form of government. On July 13, 1787, Congress passed the celebrated ordinance known as the “Ordinance of 1787,” for the government of this country, then called the “Northwest Territory.” In 1788 the first officers were appointed. In 1790 the country now Illinois, was established as St. Clair County, named after General Arthur St. Clair, the first governor of the Northwest Territory. In this year Illinois County became part of Indiana Territory, and in 1809 the country west of the Wabash, north of the Ohio and east of the Mississippi, was erected into Illinois Territory, which was divided into two counties-Randolph and St. Clair-the territory now Rock Island County forming part of St. Clair County. On September 14, 1812, our county became a part of Madison County, and on January 31, 1821, we were made a part of Pike County. This was the first county erected by the State of Illinois. January 28, 1823, Fulton County was erected from Pile County, and we became a part of the former, and so remained until January 13, 1825, when we became a part of Peoria County. On February 17, 1827, Jo Daviess County was erected from Peoria County, and Galena became our county seat. We remained part of Jo Daviess County until 1833, when Rock Island County was organized, with the boundaries as they exist today. The ordinance of 1787 provided for the forming of one or two states out of the territory now the states of Wisconsin and Illinois. The ordinance provided that the northern boundary of the territory now Illinois should be an east and west line drawn through the southerly bend or extreme of Lake Michigan. Had this provision been carried out when Illinois was erected into a state in 1818, that part of Rock Island County east of Moline would now be in Wisconsin. When the bill to admit Illinois as a state was presented to Congress and referred to the committee, our northern boundary was as defined in the ordinance of 1787, which would have left out of our state the counties of Lake, McHenry, Boone, Winnebago, Stephenson, Jo Daviess, Carroll, Ogle, DeKalb, Kane, De Page, Cook, Lee, Whiteside, and also a portion of Kendall, Will, La Salle and Rock Island Counties. In 1816 the United States made a treaty with the Ottawa, Chippewa and Pottawatomie Indians and it became necessary to establish the point where a line “due west from the southern extremity of Lake Michigan” would strike the Mississippi River. Such a line was surveyed by John Sullivan in 1818, and a monument was erected at its terminus, “on the bank of the Mississippi River near the head of Rock Island.” This place is between Seventeenth and Eighteenth streets in the City of Moline, and is now occupied by the Moline City Waterworks. Alexander Pope, the representative from Illinois in Congress, was fully alive to the interests of his constituency. Mr. Pope asked to strike out of the bill the description which bounded Illinois on the north by a line drawn directly west from the southerly boundary of Lake Michigan, and insert the following: “Beginning at the mouth of the Wabash River, thence up the same and with the line of Indiana to the northwest corner of said state; thence east with the line of the same state to the middle of Lake Michigan; thence north along the middle of said lake to north latitude 42 degrees 30 minutes; thence west to the middle of the Mississippi River, and thence down along the middle of that river to its confluence with the Ohio River, and, thence up the river along its northwest shore to the beginning.” This carried. The northern boundary of Illinois was thus fixed, and was made to include a strip of land sixty-one miles nineteen chains and thirteen links wide, extending from Lake Michigan to the Mississippi River, embracing a surface of 8,500 square miles. The line surveyed by Sullivan in 1818 was accepted as a true line until 1833, when Captain Talcott, while making the survey of the Ohio-Michigan boundary, was instructed to ascertain the exact point on the Mississippi River which is due west from the southern extremity of Lake Michigan. He established this point as being “about seven miles north of the fort (Armstrong) on Rock Island.” From 1829 to 1848 the question of adding these fourteen northern and a portion of the four other Illinois counties to Wisconsin was a prominent one in the northern part of the state. Strange to say, for many years most of the people living in the northern part of the state were in favor of being added to Wisconsin; but when Wisconsin was admitted as a state in 1848 its southern boundary line was fixed at the heretofore established northern boundary of the State of Illinois, and thus was forever settled what for many years was a subject of much dispute.
Source: Historic Rock Island County, pub. Kramer & Company, Rock Island, Illinois, 1908