Secretary of the Interior Stewart and Lee Udall hike along the Chesapeake and Ohio Canal in Washington. They are on a visit to authorize the establishment of a Chesapeake and Ohio Canal National Historical Park in Maryland, April 1961.
The Mexican-American border is constantly changing, not just by treaty, but by the persistent erosion of the Rio Grande. As a natural boundary, the river's channel determines the technical border between the two countries. Historically, the Rio…