Approximate location — plotted from published sources, not a site visit, and not a guarantee of access.
Calabasas began as an O’odham and Spanish colonial place on the upper Santa Cruz River. A Mexican presidio, U.S. Fort Mason, and a customs post followed before the place faded. The principal standing ruins are Mission San Cayetano de Calabazas, now a unit of Tumacácori National Historical Park. The fragile mission is closed except on scheduled guided tours; the wider former townsite is largely private or vacant ground in the Rio Rico area.