Early in 1945 Oak Ridge began shipping bomb-grade U235 to Los Alamos. Between shipments Groves took no chance with a substance far more valuable gram for gram than diamonds. Although the Army had condemned all the land and ejected the original inhabitants from the Clinton reservation area, at the dead end of a dusty reservation back road cattle grazed on a pasture beside a white farmhouse. A concrete silo towered over the road which was sheltered by a steep bluff. From the air the scene resembled any number of small Tennessee holdings, but the silo was a machine-gun emplacement, the farm was manned by security guards, and built into the side of the bluff a concrete bunker shielded a bank-sized vault completely encircled with guarded walkways. In this pastoral fortress Groves stored his accumulating grams of U235. Armed couriers transported it as uranium tetrafluoride in special luggage by car to Knoxville, where they boarded the overnight express to Chicago. They passed on the luggage the next morning to their Chicago counterparts, who held a reserved space on the Santa Fe Chief. Twenty-six hours later, in midafternoon, the Chicago couriers debarked at Lamy, the stranded desert way station that served Santa Fe. Los Alamos security men met the train and completed the transfer to the Hill, where chemists waited eagerly to reduce the rare cargo to metal.