From the record
“The Comanche Crossing of the Kansas Pacific Railroad is a site where the last spike was driven into the first continuous transcontinental railroad on August 15, 1870. The site is east of Strasburg, Colorado, near railroad mile marker 602.”
Wikipedia article Comanche Crossing of the Kansas Pacific Railroad, CC BY-SA 4.0.
One of 26 National Register listings published here for Arapahoe County · listed in 1970 · category: Site.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service