There were five former U.S. presidents who were alive during all or part of the U.S. Civil War. They were: Martin Van Buren (8th), John Tyler (10th), Millard Fillmore (13th), Franklin Pierce (14th), and James Buchanan (15th).

Only John Tyler had an active role in the Confederate government.

John Tyler was the 10th President of the United States, serving from 1841 to 1845, following the death of William Henry Harrison. Tyler was also a former member of the U.S. House of Representatives, serving from 1815-1821 and again from 1829-1837. [1]

When states began to declare secession from the Union in late 1860/early 1861, Tyler was a key part of a peace convention that attempted to head off the war in early 1861. [2] When that attempt failed, he was elected to the Virginia Secession Convention and voted with the majority for the State of Virginia to secede from the Union. [3]

He served as a delegate to the Confederate Provisional Congress in November of 1861. [4] He was later elected to the newly formed Confederate House of Representatives, but died in January of 1862, shortly before the new legislature’s first session.

Franklin Pierce (14th U.S. President, 1852-1857) was also accused of being a Confederate sympathizer, due in part to his friendship with Confederate President (and his own former Secretary of War) Jefferson Davis. [5] However, Pierce was not active in the Confederate government in any way.

[1] Archives of the U.S. House of Representatives, Biography of John Tyler, https://history.house.gov/People/Detail/23187

[2] Samuel Eliot Morison, "The Peace Convention of February, 1861" https://www.jstor.org/stable/25080547?read-now=1&seq=1#page_scan_tab_contents

[3] University of Richmond, Documents of the Virginia Secession Convention, https://secession.richmond.edu/queries/delegates.php?keyword=&delegates%5B%5D=tylerj&formType=Delegates&Submit=&start=1&formType=Delegates&order=date&direction=ascending

[4] Journal of the Congress of the Confederate States of America, November 18, 1861, https://memory.loc.gov/cgi-bin/query/r?ammem/hlaw:@field(DOCID+@lit(cc00199))

[5] Former President Franklin Pierce Defends Himself Against Treason Charges Brought by William H. Seward, March 1862, https://www.shapell.org/manuscript/former-president-franklin-pierce-accused-of-treason-by-seward/