A garrison of  (generally fifty) Spanish soldiers and their families, a presidio was sometimes fortified and sometimes it was not.  The Tubac, Altar, and Terrenate presidios spoken of in this diary, and located in Sonora, did not have forts.  The new California presidios were generally built with fortifications.  Aside from the soldiers and their families, the presidios always attracted other people such as farmers and busimen who could trade there products there, and, especially in the Apache country of Sonora, felt safer living at the presidio than away from it. (D.G.)