[Letter] 1840 May 12, Gambier, [to] Curtis Esq., Mt. Vernon / C[hauncey] Colton.

Chicago citation style
Colton, Chauncey, 1800-1876. [Letter] 1840 May 12, Gambier, [to] Curtis Esq., Mt. Vernon / C[hauncey] Colton.. 1840-05-12. Retrieved from the Digital Public Library of America, http://cdm.lib.lehigh.edu/cdm/ref/collection/letters/id/2326. (Accessed December 11, 2018.)
APA citation style
Colton, Chauncey, 1800-1876, (1840-05-12) [Letter] 1840 May 12, Gambier, [to] Curtis Esq., Mt. Vernon / C[hauncey] Colton.. Retrieved from the Digital Public Library of America, http://cdm.lib.lehigh.edu/cdm/ref/collection/letters/id/2326
MLA citation style
Colton, Chauncey, 1800-1876. Retrieved from the Digital Public Library of America <http://cdm.lib.lehigh.edu/cdm/ref/collection/letters/id/2326>.
Note: These citations are programmatically generated and may be incomplete.