Officially called the "Goshen Branch", named after the small town of Goshen, Idaho, this branch formed a line between the cities of Firth, Idaho and Ammon, Idaho. The line operated for around 50 years and in the mid-1970s it was shut down and the tracks removed. Traffic was diverted to the UP mainline, running from Firth to Idaho Falls.

Only a few markers of this line are available from ground level, such as a grain elevator south of Ammon with slight signs of the right-of-way running beside of it. Most of the ROW has been reverted back to farm land and is hardly recognizable, however aerial photography clearly shows the corridor in many places along the line where property lines end along it and even roads built on top of it.

As of 2011, large piping, which is assumed to be sewage piping, is being buried along the vacant portions of the ROW south of Ammon.