"Flag Stop at Malta Bend" tells the story of America's railroad trains. The program focuses on the small town of Malta Bend, Mo., where train tracks converge from all directions. Other highlights . . . Baltimore: The historic 1831 race between Peter Cooper's "Tom Thumb" engine and a horse-drawn carriage is re-created. Washington, D.C.: Cameras on a special sightseeing train record some of Washington's landmarks. New York City: The activity in Pennsylvania Station is seen. San Gabriel Cal.: We visit movie-director Ward Kimball, who has set up a private railroad in his back yard. Sierra Valley, Cal.: Viewers are taken for a ride on the California Zephyr, a speedy streamliner.