didn't they used to call U.S. routes "federal highways?" Before the Interstates?

Answer 1

Before the Interstate Highway system brought fast, limited access highways to the United States, there was, and still remains, another nationwide system of highways that enabled travelers to follow standardized routes to any part of the nation. This system, known as the United States Highway System or simply as "US" highways, was the first time in history that a national standard was set for roads and highways. This system of highways existed

This system was created by the Federal Aid Highway Act of 1925 as a response to the confusion created by the 250 or so named many named highways, such as the Lincoln Highway or the National Old Trails Highway. Instead of using names and colored bands on telephone poles, this new system would use uniform numbers for inter-state highways and a standardized shield that would be universally recognizable. The most important change was that this new system would be administered by the states, not by for-profit private road clubs. Even then, people decried the idea of giving roads numbers since they felt numbers would make highways cold and impersonal.

Answer 2

They still do. A US Highway Route is different than an Interstate Route. Odd numbered routes run north and south and even numbered run east and west. Interstate highway with three digits indicate: starts with odd number, leads into central business district; starts with even number, goes around central business district.

Answer 3

I don't know

I think Eisenhower made the Interstates

Answer 4

Before that they were called trails!