Robinson moved to San Diego in the Spring of 1850 and was one of the few lawyers there, and was fluent in Spanish, so specialized in land law.

Robinson was one of the few Americans to speak out against U.S. recognition of Mexican land grants in the Treaty of Guadalupe Hidalgo.

He said: These acts of national robbery, desperate like a vampire, draining the last dollar from the impoverished inhabitants of our State, without law and contrary to law.The land grants were huge and given to a few favored people by local Mexican officials.

Robinson was city treasurer in 1851, school commissioner in 1854, district attorney in 1852–1855, and president of the board of trustees for San Diego during 1853–1855.

This adobe has been reconstructed and serves as Old Town State Historic Park headquarters, and is open to the public.

With his associate Louis Rose, Robinson founded the San Diego and Gila Railroad and was elected its president in 1855.

His obituary in the San Diego Herald said that he was: the most prominent man during the last six years, in every enterprise which relate to our prosperity and advancement.Robinson's estate wasn't settled until 1903, after all his children died.