Is There a Montreal in California? No—Only in Quebec

No. There is no city, town, or census-designated place named "Montreal" in California (or any US state).

Montreal is a major city in the province of Quebec, Canada — the second-largest Canadian city (~1.8M metro), cultural capital of French Canada.

Possible Confusions:

• Montclair (San Bernardino County, CA / Essex County, NJ)
• Montebello (Los Angeles County, CA)
• Montara (San Mateo County, CA)
• Montrose (LA County, CA / Colorado / Pennsylvania)
• Montalvo (Ventura County, CA)

California has many Spanish/Californio names (San, Santa, Los, La, El, Monte, Rio, Sierra) — but Montreal is distinctly French-Canadian (Mont Royal = Mount Royal).