If you don’t yet know your ancestor’s address in 1940 for purposes of finding him or her in the 1940 census, here’s a resource for you:
Ancestry.com’s collection of 1940s-era records is free to search through Tuesday, April 10. The collection includes birth, marriage, death and military records from the 1940s, plus US city directories and the 1930 US census.
Note this collection doesn’t include the 1940 census. Ancestry.com’s 1940 census is a separate records collection, available free here.