Peoria is a city in and the county seat of Peoria County, Illinois, United States, and the largest city on the Illinois River. Established in 1691 by the French explorer Henri de Tonti, Peoria is the oldest European settlement in Illinois, and is named after the Peoria tribe. As of the 2010 census, the city was the seventh-most populated in Illinois (and the third largest outside of Chicagoland), with a population of 115,007. The Peoria Metropolitan Statistical Area had a population of 373,590 in 2011. Peoria had a population of 118,943 in 2010, when far northern Peoria was also included. Peoria is the headquarters for Caterpillar Inc., one of the 30 companies composing the Dow Jones Industrial Average.
Peoria is one of the oldest settlements in Illinois, as explorers first ventured up the Illinois River from the Mississippi. The lands that eventually would become Peoria were first settled in 1680, when French explorers René-Robert Cavelier, Sieur de La Salle and Henri de Tonti constructed Fort Crevecoeur. This fort would later burn to the ground, and in 1813 Fort Clark, Illinois was built. When the County of Peoria was organized in 1825, Fort Clark was officially named Peoria.
Peoria was named after the Peoria tribe, a member of the Illinois Confederation. The original meaning of the word is uncertain; a recent proposal suggests a derivation from a Proto-Algonquian word meaning "to dream with the help of a manitou".
Peoria was incorporated as a village on March 11, 1835. The city did not have a mayor, though they had a village president, Rudolphus Rouse, who served from 1835 to 1836. The first Chief of Police, John B Lishk, was appointed in 1837. The city was incorporated on April 21, 1845. This was the end of a village president and the start of the mayoral system, with the first mayor being William Hale.