|Elevation||296 m (971 ft)|
|Time zone||Pacific (PST) (UTC-8)|
|• Summer (DST)||PDT (UTC-7)|
|GNIS feature ID||1660703|
The area was a former major wine producing district in the Cucamonga Valley AVA region, with the Italian Vineyard Company based here. By 1917 the Cucamonga-Guasti vineyards spanned over 20,000 acres, and Secondo Guasti was advertising his vineyard as "The Largest in the World." 
The community changed its name from Zucker to Guasti after Secondo Guasti, founder of the Italian Vineyard Company, which operated in the area. The Guasti post office opened in 1910.
This small Post Office, which is located across the street from the Ontario International Airport, was made famous by Default Radio co-host Lucky225 and Doug from DougTV. Lucky225 and Default Radio used the "Default Mail Box" - P.O. BOX 1111, Guasti, CA 91743. Doug further popularized it in Doug TV Episode 1
- "US Board on Geographic Names". United States Geological Survey. 2007-10-25. Retrieved 2008-01-31.
- Inside The Inland Empire: "The Wineries of Rancho Cucamonga are back.", 9 May 2007.
- Durham, David L. (1998). California's Geographic Names: A Gazetteer of Historic and Modern Names of the State. Quill Driver Books. p. 1424. ISBN 1-884995-14-4.
- ZIP Code Lookup
- IPTV Archive / DougTV
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