From the marker:
This old covered bridge and parts of the abandoned right-of-way are reminders of the Vancouver, Victoria, and Eastern Railway (VV&E), a subsidiary of the American-based Great Northern Railway. Between 1907 and 1914, the VV&E pushed northward, following the Similkimeen River.
James J. Hill, the famous 'Empire Builder' of the GNR, had plans to link the mineral-rich southern Interior with the coast but was locked in a struggle with the mighty Canadian Pacific Railway (CPR), pursuing the same idea, The intense rivalry ended when Hill died in 1916, his grandiose scheme dying with him, leaving the field open to his old rival, the CPR who finally completed the southern route to tidewater.
While researching this sign, I cam across a webpage by Jean-Francois Brulotte, on it he has this picture taken in the late 1950's or early 1960's showing that the original marker for this location was an old style 'Stop of Interest' sign. I believe you can see in the photo the Similkameen in the background. A friend of his, Rich Bauer, acquired the photo as a slide at a garage sale.