After General Andrew Jackson declined appointment as Secretary of War, Monroe turned to South Carolina Congressman John C. Calhoun, leaving the Cabinet without a prominent Westerner. In late 1817 Rush became the ambassador to Britain, and William Wirt succeeded him as Attorney General.[80] With the exception of Crowninshield, the rest of Monroe's initial cabinet appointees remained in place for the remainder of his presidency.[81]

Missouri Compromise
Main article: Missouri Compromise
In February 1819, a bill to enable the people of the Missouri Territory to draft a constitution and form a government preliminary to admission into the Union came before the House of Representatives. During these proceedings, Congressman James Tallmadge, Jr. of New York "tossed a bombshell into the Era of Good Feelings"[82] by offering the Tallmadge Amendment, which prohibited the further introduction of slaves into Missouri and required that all future children of slave parents therein should be free at the age of twenty-five years. After three days of rancorous and sometimes bitter debate, the bill, with Tallmadge's amendments, passed. The measure then went to the Senate, which rejected both amendments.