Walker was appointed Governor of Kansas in 1857 by President James Buchanan but resigned shortly after due to his opposition to the administration-sponsored pro-slavery Lecompton Constitution.

Initially educated at the Bellefonte Academy,[1] Robert Walker graduated in 1819 at the top of his class at the University of Pennsylvania where he was a member of the Philomathean Society.

However, his brother Duncan (a former Mississippi legislator) moved to Texas in 1834 for health reasons, where he became involved in land speculation and the growing independence movement.

[2][3] Robert Walker became politically prominent during the Nullification Crisis of 1832, even arguing the federal government's right to coerce rebellious states and earning praise from former President James Madison.

[4] Walker served in the United States Senate as a Unionist Democrat from 1835 to 1845, winning re-election by a two to one margin over Sergeant S. Prentiss, as well as convincing Mississippi legislators to adopt resolutions denouncing nullification and secession as treason.

He also worked for the nomination and election of James K. Polk in 1844, in part because President Martin Van Buren opposed annexation.

As a Mississippi senator and slaveholder himself, Walker passionately defended slavery, while also opposing the African slave trade and favoring gradual emancipation and the efforts of the American Colonization Society.

[citation needed][8][9] Walker also claimed that independent Texas had to be annexed to prevent it from falling into the hands of Great Britain, which would use it to spread subversion throughout the South.

He warned Northerners that if Britain succeeded in undermining slavery, the freed slaves would go north, where "the poor-house and the jail, the asylums of the deaf and dumb, the blind, the idiot and insane, would be filled to overflowing.

He and Edwin Stanton became Pittsburgh's lawyers in the city's (and Pennsylvania's, represented by its attorney general Cornelius Darragh) litigation against the Wheeling Suspension Bridge in the United States Supreme Court.

[citation needed] He was appointed governor of Kansas Territory on May 27, 1857, by President James Buchanan, but resigned in December because of his opposition to the Lecompton Constitution.

[16] In a resignation letter to Secretary of State Lewis Cass dated December 15, 1857, he cited clear voting fraud and improper political pressure from the Administration.

Despite his status as a former Mississippi senator and slave owner, as a Southern Unionist Walker supported the Union cause during the American Civil War.

[17] Walker resumed his Washington, D.C., law practice upon returning from Europe in November 1864, and also continued publishing on financial topics until his death in the national capital five years later.

A merchant vessel named Robert J. Walker was constructed in 1943, and served until its sinking by a German U-boat off the coast of Australia the following year.