From the record
“The San Luis Southern Railway Trestle, in Costilla County, Colorado near Blanca, Colorado, was built in 1910. It was listed on the National Register of Historic Places in 2004.”
Wikipedia article San Luis Southern Railway Trestle, CC BY-SA 4.0.
One of 13 National Register listings published here for Costilla County · listed in 2004 · category: Structure · built in 1910.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service