Rancho Cucamonga is a city in San Bernardino County, California, United States. As of the 2000 census, the city had a total population of 127,743. By July 1, 2002 Census the fast-growing city's population had reached 143,711. By early 2006, the city's estimated population had reached over 170,000 people. Rancho Cucamonga apartments for rent comparison page shows most up to date rent information on Rancho Cucamonga apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.