UP 1957 (SD40N) sorts a cut of cars in the Union Pacific's North Yard in Denver, Colorado.

Union Pacific AC4400CW 6279 shows its heritage as Southern Pacific 248, built by GE in June 1995, and spotted at the UP's Dolores Yard. (Carson, California – October 1, 2008)

On Cinco de Mayo, Union Pacific railroad local LOW10-06, with UP GP40-2 1442 (ex-SSW 7279), GP60 1150 (ex-UP 1903, ex-UP 5703, née-SP 9600), GP40P-2 1373 (ex-SP 7601, née-SP 3198) and SD7... (more)

A pair of UP SD40N locomotives leads a transfer onto the Harbor from the CPKC back to Proviso.

UP 801 (GP38-2) pulls out a cut of gondolas at a yard in Commerce City, Colorado.

UP 801 (GP38-2) sits in a yard in Commerce City, Colorado.

UP 5654 (AC4400CW-CTE) leads a freight on the Greeley Sub past silos in Commerce City, Colorado.

The Colorado Rocky Mountains loom large above UP 2698 (AC4400CW) as it leads an oil train towards Arvada, Colorado on the Moffat Tunnel Sub.

UP 6825 (ES44AC) runs past the signal at Leyden, Colorado.

UP 8009 (ES44AC) muscles an oil can through Leyden, Colorado.

UP 8639 (SD70ACe) shoves an oil can train through a very snowy Tolland, Colorado.

UP 8835 shoves on the rear of a long WB just west of the Palm Springs crossovers.

UP 7328 leads the westbound ZG4CI downgrade at El Casco.

UP 4533 (SD70M) leads an officer train through Barbara's Gulch between Chemical and Rocky, Colorado.

UP 2698 (AC4400CW) leads an oil can train through Leyden, Colorado.