The Utah and Northern Railway is a defunct railroad that was operated in the Utah Territory in the western United States during the late 1860s and early 1870s. It was a narrow gauge line built by the Mormon Co-op as a spur of the Union Pacific portion of the transcontinental railroad. The line went northward from the Union Pacific line, but construction halted in 1874 at the present Utah-Idaho border.
The discovery of gold in the Idaho Territory resulted in an increasing demand for movement of people and goods into the territory. In 1877, Jay Gould acquired the line and extended it northward into Idaho along the canyon of the Portneuf River into the Snake River Plain. The line was extended northward into Montana in 1880
