Where the US transcontinental railroad was completed in 1869. The National Park Service runs the Golden Spike National Historic Site there, complete with a museum and operational replicas of the original locomotives, the Central Pacific's Jupiter and the Union Pacific's #119. (The Central Pacific was building eastward from California, while the Union Pacific built westward.)

Note the differences in the locomotives' smokestacks. The wide funnel on the Jupiter was due to its being fueled by wood, while #119 was coal-fired. A screen over the top of the wide funnel on wood-burning locomotives was supposed to stop sparks, and thus keep the countryside from catching fire. It didn't always work...

Ironically, the railroad itself is abandoned; it was bypassed in 1904 by the Lucin Cutoff laid directly across the Great Salt Lake. The rails were ripped up in 1942 for the war effort, but a mile and a half was relaid for the park in 1969.