Santa Fe Trail Marker & Cow RPPC Antique Frontier Photo  1907 – Divided Back Post Cards In 1907, Congress lightened up on the address-only limitations, allowing for messages along with the address and ushering in the era of the Divided Back Post Card.
1901 – Undivided Post Cards In late 1901, Congress passed legislation that allowed private printers to call their cards Post Cards instead of including the long and cumbersome phrase from the Private Mailing Cards.
From the Fifty-Sixth Annual Report, Fiscal year ended February 29, 1940
You wouldn’t believe how many articles like this exist. Lets do better Las Animas.