My mother's father's side has always been very difficult to research, given that they were a bunch of late-19th century immigrants from countries whose records were not well-kept. My grandfather's mother was Isabel Mary Azevedo, born 10 Jun 1910 in Dos Palos, Merced. Her parents were Manuel M. Azevedo and Maria Reis Mattos, both immigrants from the Azores, Portugal. The only good record of Isabel's parents I've found is the 1920 census on Ancestry.com, in which Isabel is listed with her parents and many siblings. I have reason to suspect Manuel was a dairy farmer, as his grandson, my grandpa, grew up on a dairy farm. The number of farmers named Manuel Azevedo living in that area is a problem in and of itself, but mine lived from about 1870-before 1929. Apparently, his wife Maria lived from about 1878-1930. To add insult to injury, there is another Manuel M. Azevedo with the same dates of birth and death, but he's buried in Sacramento, not Merced, and has nothing to do with my great-great-grandfather. No idea which island he came from, but if I had to guess, I'd say Pico.
I don't have money for subscriptions right now, so if you have free resources, I'd be grateful. I'll accept .pdf links, but because I research primarily from my phone, they can be a pain.