US Sea Post Service New York & Canal Zone
Sea mail between New York and the Canal Zone started as the Railway Mail Service on Oct. 31, 1907, then went under the control of the Sea Post
Service in 1912, and ended in 1917 when the U.S. entered World War I. The service was reestablished as the Railway Mail Service in 1921.
It was then re-established in 1921 as the Railway Mail Service until 1925 when it rejoined the Sea Post Service and continued until 1932.
Source reference:
Cockrill, Booklett No 54 und No 55
Hosking, Seaposts of the USA
Postage paid commercial postcard with postmark CZ2 to Cockrill. Postmarked March 13, 1919 (color direction North) and postmarked "R.P.O." (Railway Post Office). Addressed to Davenport, Iowa.
Postage paid commercial postcard with postmark CZ2 to Cockrill.Postmarked Feb. 03, 1912 (southbound) and stamped "R.P.O." (Railway Post Office). Addressed to New York, N.Y.
Overstamped commercial postcard with postmark CZ3 to Cockrill. Postmarked 03. June 1913 with 3 in the killer (direction North) and cancelled with "R.P.O." (Railway Post Office). The ship for this number is not known. Addressed to Bremen, Germany.
Postage paid commercial postcard with cancellation CZ3B to Cockrill. Cancelled 05 April 1913 with 2 in the killer. The ship for this number is not known. Addressed to Mayfield, Ky.
Overstamped commercial postcard with postmark CZ4 to Cockrill. Postmarked 18. December 1922 with 3 in the killer (northbound) and cancelled with "R.P.O." (Railway Post Office). The ship for this number is not known. Addressed to New York, N.Y.
Overstamped commercial postcard with postmark CZ4 to Cockrill. Postmarked 18 December 1922 with 3 in the killer (northbound) and cancelled with "R.P.O." (Railway Post Office). The ship for this number is not known. Addressed to New York, N.Y.
Overstamped commercial postcard with postmark CZ6 to Cockrill. Cancelled 10. November 1927 with 7 in the killer. The ship for this number is the "S.S. Pres. Harrison." Addressed to New York, N.Y.
Postage paid collector's cover with postmark CZ8 to Cockrill. Postmarked 02. February 1930 with 17 in the killer. The ship for this number is the "S.S. Pres. Wilson". Franked with one of the stamps with "Nebr." overprint. Addressed to San Francisco, Calif.
Postage paid collector's cover with postmark CZ9 to Cockrill. Postmarked 16. January 1930 and exists only with this date. The ship is the "S.S. Pres. Fillmore." Addressed to San Francisco, Calif.
Postage paid commercial cover with postmark CZ10 to Cockrill. Cancelled 30. November 1927 (sailing north) with 1 in the killer. The ship is the "S.S. Cristobal". Addressed to New York, N.Y.
Postage paid commercial cover with postmark CZ11 to Cockrill. Postmarked 23. May 1929. The ship is the "S.S. Pres. Johnson." Addressed to Wilmington, Delaware.
Underpaid collector's cover with provisional postmark. Postmarked 11. October 1928. The ship is the "S.S. Pres. Harrison." This postmark exists only with this one date. Addressed to Philadelphia, Pa.
Postage paid collector's cover with provisional postmark. Postmarked 04 February 1929. The ship is the "S.S. Pres. Johnson". This postmark exists only with this one date. Addressed to San Francisco, Cal.
Postage paid collector's cover with provisional postmark. Postmarked 25. April 1929. The ship is the "S.S. Ruth Alexander", which replaced the ship "S.S. Pres. Adams", due to an accident in February 1929. This stamp exists only with this one date. Addressed to Forks, N.Y.
