Gilbert is a town in Maricopa County, Arizona, USA. It was founded on July 6, 1891 as a rail siding for Arizona Eastern Railway, it was incorporated as the Town of Gilbert in 1920. Gilbert is still incorporated as a town rather than as a city; it has the highest population of any area incorporated as a town in the United States. Gilbert was also the fastest-growing place among all cities and towns in Arizona of any size between 1990 and 2000. A 2006 real estate survey has estimated the population of Gilbert, Arizona at 191,517.