who was Polk?
James Knox Polk was the eleventh American President (about 20 years before before Lincoln) who carried out the Mexican-American war and greatly expanded the territory of the Unitied States westward, beyound the Louisiana Purchase which ended at the rockies. He also negotiated the boundary of the Oregon Territory (which forms present Washington, Oregon and Idaho, with Canada, which Britain had claimed.
For more about him, see
http://en.wikipedia.org/wiki/James_K._Polk