One of the census' I found lists my great grandparents language as "Russ-Lettish". Family history says they were from Lithuania, but Lettish seems to suggest Latvia.

Any ideas? Thanks.

Apparently 'Lettish' was a generic term to cover Lithuanian, Latvian and (I think) Estonian. If your family consider themselves Lithuanian then that is what they were. When Russia took over all that area people fought hard to keep their own identity even though Russia would not them teach Lithuanian in schools.
Janice

Interesting. Thank you. This helps in my research.