1 is a historic railroad tunnel located about 40 miles (64 km) north of Seward, Alaska, in the Placer River Valley, Kenai Peninsula.

[2] In 1903, the Alaska Central Railroad began a rail project north from Seward.

The company encountered the most significant geographic obstacles to construction between 47 and 53 miles (85 km) north of Seward, a section known as the "Loop District", where the line would need to cross a high-point in the Kenai Mountains and avoid the paths of two glaciers.

Between March and November 1905, engineer Frank Bartlett determined sites for the structures needed to complete the route.

With rising costs associated with keeping the tunnel operable and the task of replacing many declining trestles, the railroad undertook a $1 million project in 1951 to relocate the route around Loop District between Miles 47.5 and 50.8 north of Seward.