Gilbert is a town in Maricopa County, Arizona, United States. Located southeast of Phoenix, Gilbert is home to 288,128 residents. It is the fifth-largest municipality in Arizona. Nearly a third of Gilbert residents are under the age of 18. As Gilbert approaches buildout, the population is expected to reach 330,000. Incorporated on July 6, 1920, Gilbert was once known as the "Hay Shipping Capital of the World".