UP 7773 (AC45CCTE) runs over Sand Creek at is heads towards the North Yard in Denver, Colorado.

UP 5530 (ES44AC) leads a stack train solo as it enters the 36th Street Yard in Denver, Colorado.

Snow is falling in downtown Denver, Colorado as the Iowa Interstate 'Hawkeye' Business Car IAIS 800342 passes the Colorado Rockies baseball stadium while it backs into Denver's Union Station.

RTD commuter train #4025 (Hyundai Eagle P3) runs through the North Yard at sunrise.

UP 7528 (ES44AC) gets repositioned in the North Yard after getting serviced at the fuel island.

UP 688 (GP38-2) runs long hood forward in a Siamese configuration as it works shuffling cars in the North Yard in Denver, Colorado.

UP 663 (GP38-2) must have spent some time in California before arriving in the North Yard in Denver, Colorado.

Two crewmembers walk back to the operations building in the Union Pacific's North Yard in Denver, Colorado.

RTD of Denver commuter train #4002 (Hynda Eagle P3) spits the catenary structures as it runs between Denver and Arvada, Colorado.

Fresh snow on the tracks and sub-freezing temperatures creates the perfect conditions for sunrise whippage as the Winter Park Express Ski Train leaves Denver for the ski slopes in the Rocky Mounta... (more)

Amtrak engine #170 (P42DC) leads the Winter Park Express Ski Train through the signal bridge at sunrise in the North Yard in Denver, Colorado.

UP 1826 (SD40N) works the ladders in the North Yard in Denver, Colorado.

UP 7388 (ES44AC) leads an oil can train west on the Moffat Tunnel Sub out of Denver, Colorado.

UP 7762 (AC45CCTE) joins other heavy units at the servicing island in the North Yard in Denver, Colorado.

RTD of Denver commuter train #4002 (Hyundai Eagle P3) runs between Denver and Arvada.