Rhode Island Tercentenary Issue First Day Cover
300th Anniversary of the Settlement of Rhode Island
Issued on May 4, 1936 in Providence, RI - Scott #777

Unofficial Town Cancel - Shannock, RI
1st John B. Kilton Cachet - Planty 777-61g

The Shannock Post Office, (Richmond Township, Washington County) was established on October 6, 1884 under Postmaster Charles E. Sullivan. The Post Office is currently in operation under Postmaster Terry L. Place appointed on February 24, 2001.

The Post Office was originally established as Shamrock Mills, under Postmaster Charles Clark on June 26, 1839. It name was changed to Shannock Mills on January 22, 1861 and it became Shamock for 11 days on October 6, 1884. It's name was officially changed to Shannock on October 17, 1861. This appears to be due to clerical error on the part of Postal authorities in Washington, D.C.

Sources:
Check List of Rhode Island Post Offices 1790-1994 - Del Beaudreau
Rhode Island Postal History: The Post Offices - Merolla, Jackson & Crowther