Gertrude Boyden/York/Lambert

My grandmother died in 1926. My grandfather, Alvia F. York Sr., remarried 9 Nov., 1929 to Gertrude E. Boyden in Portland, Maine. I believe she was from Bangor. My father and his sister were living with their grandparents and did not know Gertrude. Some time about 1930 Gertrude and Alvia were reported to have had a child (a son I think). The marriage did not last long and on 17 Oct 1935 Gertrude married Leo E. Lambert in Portland. I believe Leo died in Dayton, Maine (York County) on 1 June 1979. End of story. I would like to Can anyone tell me which cemeteries are in the Dayton area? Anyone with a portland city directory from 1930's? Has anyone got a copy of the 1930 or 1940 census for that area? I would really like to find the child Alvia and Gertrude had. He/She probably was adopted by Leo Lambert.