Union Pacific No. 18 is an 8,500 horsepower gas turbine-electric locomotive (GTEL) built by General Electric (GE) in August 1960 for the Union Pacific Railroad (UP). It was part of the third-generation of three generations of GTELs built for the UP between 1952 and 1961 that were initially meant to replace their 4-8-8-4 "Big Boy" and 4-6-6-4 "Challenger" type steam locomotives. It was used in regular freight service by the UP until it was officially retired from service in February 1970 along with the other GTELs in favor of conventional diesel locomotives.
After its retirement, it was placed in storage until eventually being donated in 1992 to the Illinois Railway Museum in Union, IL. It later arrived at the museum in 1993 and has remained on outdoor static display ever since. It is also one of only two UP third-generation GTELs that have been preserved, the other one being No. 26, which is on static display at Union Station in Ogden, UT. All of the first and second-generation GTELs, as well as the experimental coal turbine No. 80, were eventually scrapped after retirement.