We’re a little late to observe the centennial of a major event in U.S. railroad history, but there is still time to get covers with the pictorial postmark: One of the last great train robberies. Four Southern Pacific Railroad workers were murdered on October 11, 1923, during what became known as “The Tragedy at Tunnel 13” in the Siskiyou Mountains of Oregon and California.

It changed the way such crimes were investigated and, although it took four years, the three thugs — three brothers — were eventually caught.

Both the U.S. Postal Service and the Smithsonian’s National Postal Museum have much, much more on this. You’ll find information on how to get the special postmark on the Museum’s virtual exhibit, near the bottom of the “Resources” page. Pictorial and commemorative postmarks are supposed to be available for 30 days after the date, which gives us until November 11 to request this one.