(Mail Routes) Military Supply Route to Fort Yuma by Colorado Steam Navigation Company. Cover addressed to "Lieut Beekman Du Barry, 3rd Artillery U.S. Army, Care of Major Cook, U.S. Quarter Master" in San Francisco, franked with 1851 3¢ dull red two singles tied by "Philadelphia, Pa., Jul 3" cds paying the 6¢ trans-continental rate, Post Office Box "771" pencil notation for delivery (partially erased), forwarded to Fort Yuma, California with part of original address lined out, small repair at top and top backflap partly missing (affecting "…ington House" cameo design), Very Fine, one of the great rarities of the West. Estimate  $3,000 - 4,000. This one of only two recorded covers carried to Fort Yuma by the Colorado Steam Navigation Company on the military supply water route from San Francisco down the coast, around Baja California and up the Gulf of California, and finally up the Colorado River to Fort Yuma.This cover is dateable to 1854 given the 6¢ transcontinental rate and the fact that First Lieutenant Beekman Du Barry served at Fort Yuma from 1854 until 1856. Besides commanding Light Battery E of the Third Regiment of Artillery, Lieutenant Du Barry was also Commissary and assistant Quartermaster. As such, he designed a number of the buildings that were constructed at the post. $0 (Image)