In San Francisco squatting became a trade and in some cases a very lucrative one. An early belief held that most Mexican grants covering parts of the city were forgeries or fraudulent. This proved correct. Some claimed, and the courts later agreed, that there had existed either at the Presidio, the Mission Delores or the village of Yerba Buena a municipality known to the Spanish and Mexican laws as a pueblo or town and was entitled as such to four square leagues of land in which all inhabitants had an interest.
Because of this claim, and on the authority of the laws governing pueblos, the Mexican Alcaldes and other authorities made many grants of town lots. It was understood that these grantees, if there were a pueblo, were the absolute owners by written title to these lots, and for all the extensive tracts of land not so granted, that all the inhabitants and particularly the occupants were the owners, or, in other words, that the land was held in trust for the use and benefit of all the inhabitants.
On the other hand if the alleged grants were all invalid and there was no pueblo title it would follow that the land would be open and vacant and every man justified in settling where ever he could. The adage that possession is nine tenths of the law was therefore often voiced in the community and was the principle upon which most everyone acted until the legalities were finally settled.