The Cancel on the cover above is a "Railroad Route Agent Marking." This is different from an RPO marking which indicated a "Railroad Post Office."  The Postal Act of July 7, 1838 provided that "each and every railroad within the limits of the United States shall be a post route." The cancellation above was used between the years 1848 to 1854. 

The Providence and Worcester Railroad was chartered in 1844. The length of the road between Providence and Worcester was 43.5 miles and the length between Worcester and Boston was 44.65 miles. 

The Providence and Worcester Railroad merged with the Blackstone Canal and the Boston & Providence Railroads in 1859 with a leased line from Milford to Woonsocket. 

The Railroad was leased to the New York, New Haven & Hartford Railroad Company on December 17, 1892 for a period of 99 years.

There were over 100 small independent Railroad Companies operating in the New England and New York areas during the mid to late 19th century. Most of these small roads were consolidated with the New Haven Railroad Company.