Robert John Walker (July 19, 1801 – November 11, 1869) was an American lawyer, economist and politician. An active member of the Democratic Party, he served as a member of the U.S. Senate from Mississippi from 1835 until 1845, as Secretary of the Treasury from 1845 to 1849 during the administration of President James K. Polk, and briefly as Territorial Governor of Kansas in 1857.
As senator, Walker vigorously supported the annexation of Texas. As Secretary of the Treasury, he held responsibility for the management of funds relating to the Mexican–American War, and was involved in a bank scandal. He contributed to a bill called the Walker tariff, which reduced rates to some of the lowest in history. 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. After his retirement from politics, Walker supported the United States during the American Civil War and continued to practice law in Washington, D.C.
(the above is an excerpt from Wikipedia)