* Most of the millions of miles of interstate highways in the United States have a way of swiftly passing over the land while they appear to be passing through it. Pardon the cliche; if you drive one interstate, you've driven a dozen. * But there is a historic interstate, US Route 1, that passes slowly and bluntly through 14 states and 2,467 miles of America from Key West, Fla., to Fort Kent, Maine. Designated in 1926, Route 1 is America's first interstate. * Recently Monitor writer David Holmstrom and staff photographer Neal J. Menschel drove along most of Route 1 and discovered the lost heart of what an interstate used to be: a road with character, humanity, spirit, and some crucial problems - just like the US. * In the first of a three-part series beginning today on Page 9, Holmstrom and Menschel are on the road between Key West and Augusta, Ga.