There is lots of activity in the UP's North Yard on a cold January morning.

A fresh layer of snow in the UP's North Yard brings out the colors of the GATX and UP units waiting for assignments.

The paint on the older AC4400's have faded quite noticeably compared to the other units in the North Yard.

A fresh layer of snow has blanketed the UP's North Yard and the crew of UPY 618 (GP15-1) gets ready to sort freight cars for the next couple of hours.

There has been a noticeable increase in the last couple months of engines going through the UP's North Yard. A sign of the current booming economy.

UP 4904 pulls a smoking freight through the UP's North Yard in Denver, Colorado.

Looks like the San Luis Rio Grande Railroad's GP40FH-2 is on the move. Spotted on a train dropping off freight cars in the Denver UP North Yard.

San Luis & Rio Grande's 4144 (GP40FH-2) helps the UP pull freight into the North Yard in Denver, Colorado.

UP 688 (GP38-2) and UPY 586 (GP15-1) have somehow avoided the refresh program. Here they team up to move cars in the UP's North Yard in Denver.

With storm clouds brewing, UP 700 (GP38-2) leads two other units into the North Yard

A wide angle view of the UP's North Yard in Denver catches the heavies waiting for train assignments as well as the lighter power that work to sort cars in the yard.

It is a full house of UP power in the North Yard, including UP 1370, a former Denver & Rio Grande Western GP40-2.

CSXT 8024 paid a visit to the UP's North Yard. The SD40-2 was built in 1979 for the Louisville and Nashville Railroad and then spent a stint with the Seaboard System before joining the CSX team. ... (more)

The sorting of engines in the UP's North Yard in Denver is fun to watch. The remote engineers pull a long line of freight cars from a receiving track and then give brief spurts of power as they s... (more)