Americans have many icons. But those dealing with the exploration and expansion of the United States seem especially beloved: stagecoaches, steamboats, trains—and the railroad caboose. From the mid-19th century through the last decade of the 20th century, the “little red caboose behind the train” has had iconic qualities similar to the little red schoolhouse, being the subject of songs, books, and toys that remain popular today. So what’s the caboose, and why has this icon largely disappeared from the national …