A large wooden trestle was built in this region so early trains could pull their loads up the steep grade.  The trestle looped over itself thus reducing the incline.  The loop was touted as an engineering marvel, but was also a high maintenance item.  The Alaska Railroad also had to maintain a heating plant and two watchmen at Tunnel for the loop.

In 1951 a $1,000,000 line relocation project eliminated the famous loop between miles 47.5 and 50.8 since the new diesel locomotives were able to pull loads up the steeper grade.  This also reduced maintenance costs due to constant trestle repair as well as taking the mainline away from a snowslide area..  On November 6, the last rail was dropped in place at 11:06 a.m. and the final spike was driven by Colonel J.P. Johnson at 11:30 a.m.

Today, Tunnel is a section house that is manned year round.  Wintertime can be especially brutal with fridged winds and temperatures that dip well below zero degrees.  Caterpillars are kept ready to clear out the many avalanches.  Just north of Tunnel is a series of six tunnels encompassed within one mile and the workers do whatever is necessary to keep these clear of ice and snow.  Living conditions are harsh, but section workers make the best of it.  In their off hours, they can be seen running their snowmobiles across the countryside or crouched by an icy river panning for gold.
 
 

Tunnel #1 and the bridge located at mile post 51.8.  The gorge under this bridge is deep and very steep.	The north portal of tunnel #6.  A hi-rail shop truck is on the right and an avalanche caterpiller is on the left.	The section house for the workers.  The grade on the rail is 2.2% and the coal train typically doubles the hill in this area.