Horses came to America from Spain, England, the Low Countries, and Arabia. Here they interbred and flourished as never before. "Out of the melting pot have come four entirely new breeds that rank among the finest horses of the world. Three of them originated through the painstaking and intelligent efforts of American horsemen, one through a freak of nature." That "freak" was a little bay stallion born when George Washington was president. This chunky,...