In 1961, what did Yutan Construction purchase in order to house the construction workers who were upgrading the Stampede Trail? What did they leave behind?

Yuhan construction company purchased the Fairbanks City Transit System Bus 142 and it was left behind until when the Stampede Mine ceased operations in the 1970s

Explanation:

In 1960, Yutan Construction won a contract from the new state of Alaska to upgrade the trail as part of Alaska's Pioneer Road Program, building a road on which trucks would be able to haul ore from the mines year-round to the railroad at Lignite near the present day town of Healy. Construction was completed in 1961 after some 47.5 miles (76.4 km) of road was built but no bridges were ever constructed over the several rivers it crossed. Maintenance on the project was halted in 1963 and the route was shortly rendered impassable to large vehicles by soft permafrost and seasonal flooding.

The Fairbanks City Transit System Bus 142 is used by Yutan Construction Company to provide remote accommodations for the construction crew from Fairbanks that worked on road upgrades in 1960–1961.

All except this one bus (Fairbanks City Transit System Bus 142) were removed from the trail. Bus 142 had a broken rear axle, which caused the crew to leave it where it now serves as a backcountry shelter for hunters, trappers, and visitors.