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is one of three formerly unincorporated areas that became part of the city of Rancho Cucamonga, California, United States in 1977. The community is located in the foothills of the south face of the San Gabriel Mountain range, near Cucamonga Peak and Mount Baldy. It is located in the 91701 and 91737 zip codes. The latitude of Alta Loma is 34.122N. The longitude is -117.597W. Its lowest elevation is approximately and extends to about . The name comes from the Spanish, meaning "high hill" or "high hillside." Alta Loma had previously been known as Iamosa.
Alta Loma is one of the more affluent areas in San Bernardino County . It is almost completely residential and as per city ordinance no commercial business may exist above 19th Street, with exception to several businesses already in place when the ordinance was enacted (notably at the intersection of Lemon Avenue and Haven Avenue). In addition, homes north of Banyan Road must have a minimum of 1/2 acre lots, with the exception of the development known as Compass Rose Phase II found directly west of Chaffey College between Banyan and Wilson. Compass Rose Phase II was granted permission for smaller lots provided the development connected to city sewer systems instead of septic tanks.
The current mayor of Rancho Cucamonga, Dr. Don Kurth , lives in Alta Loma.
The community of Alta Loma is located mostly in the northwest corner of Rancho Cucamonga. The exact definitions of the three communities (Cucamonga, Etiwanda, and Alta Loma) within the City of Rancho Cucamonga are debatable; however, residents typically consider Alta Loma to be above Baseline Street (Old Route 60), between the eastern edge of Upland, California and west of Day Creek, a boundary later moved to Day Creek Boulevard when the then-future road was plotted on Chamber of Commerce maps dating to about 1980. Most street signs in the Rancho Cucamonga area stretching from Carnelian Street to Milliken Avenue, and Baseline Road to the mountains, have an Alta Loma logo.
Some residents of Rancho Cucamonga, especially those in the former Cucamonga area, have challenged the city council to get rid of the names 'Alta Loma' and 'Etiwanda,' accusing residents in those areas of keeping the names out of arrogance. The three communities incorporated after years of debate and at least one failed attempt on the ballot. Residents of Alta Loma and Etiwanda finally agreed to incorporation provided their identifying community names would be kept along with separate post offices and zip codes. In addition, businesses are permitted to use either Alta Loma or Rancho Cucamonga on letterheads, business permits, and other records.
Alta Loma is arguably the richer area of Rancho Cucamonga; however, Etiwanda and the rest of Rancho Cucamonga are expanding, and housing prices in the area continue to rise due to the constant development.
Alta Loma and the rest of Cucamonga was formerly home to old citrus groves and grape vineyards. The reason many homes above Banyan Street, in particular, have orange and lemon trees on their property may be attributed to this; many horse trails are lined with eucalyptus trees, which are former windbreakers for the groves. This also is the reason why grape vineyards can still be seen in random parts of the City of Rancho Cucamonga between office buildings and shopping malls; unfortunately these are being destroyed and replaced with housing and business developments.