Setting the Stage
"The jurisdiction of the United States…has passed the capes of Florida and been peacefully extended to the Del Norte." That's how President James K. Polk, in his December 1845 message to Congress, characterized the recent annexation of Texas by the United States. With that statement, Polk declared the boundary between Texas and Mexico was the Rio Del Norte or Rio Grande.
Sea to Shining Sea
Polk campaigned for the Presidency with a pledge to extend the United States to the Pacific Ocean. The addition of the Republic of Texas as the 28th state represented a major step toward that goal.