The city of Tustin is located in central Orange County. Tustin is bordered by the city of Santa Ana to the west, Irvine to the east and south and an unincorporated area of Orange County to the north (Tustin Foothills). The 2009 population was estimated at 74,825. Land area is about 11 square miles. Tustin was originally founded by Columbus Tustin, a northern California carriage maker, and his partner Nelson Stafford, on 1,300 acres of what had been the Rancho Santiago de Santa Ana. The orange groves and agriculture of an earlier era have now been replaced with urban development. However, the city still features an "Old Town" district with historic buildings, some dating back to the 1880s, around Main Street and El Camino Real. Tustin includes a planned community called Tustin Ranch, developed by The Irvine Company, which was annexed to Tustin in 1982. This community is built in the area surrounding the Tustin Ranch Golf Course. Tustin Foothills is an unicorporated area north of the city of Tustin is called Tustin Foothills or North Tustin by its residents. The U.S. Post Office alone uses Santa Ana as the proper mailing address designation.