FamilySearch has a searchable database of “United States Census of Union Veterans and Widows of the Civil War, 1890” on their site. This database was created of images of the extant veterans’ schedules from the US 1890 census. Not all schedules are extant–read the list before conducting a search. The schedules will provide additional service details on the veteran–or their widow. If you have a person you think was a veteran, but his name is common and you can’t “figure out which one is yours,” this database may help as it gives the residence of the individual in 1890.