Census Bureau's "By Decade" website - includes a variety of publications, questionnaires, datasets, and more
Questions asked (see questionnaire)
Name of head of family; age; sex; race; slaves; number of deaf and dumb; number of blind; number of insane and idiotic and whether in public or private charge; number of persons in each family employed in each of six classes of industry and one of occupation; literacy; pensioners for Revolutionary or military service.
Social Explorer - remote access limited to UCSD affiliates
Find all 1840 census publications in the library catalog.
Sixth Census [ C 3.14:840/1/reprint ]
Statistics of the United States of America [ C 3.14:840/2/reprint ]
Census of Pensioners for revolutionary or military services [ C 3.14:840/3 ]
Compendium [ C 3.14:840/2 ]