Treaty of Guadalupe Hidalgo, 1848
This treaty that ended the Mexican War granted the United States 500,000 square miles of land, making it a transcontinental nation. The issue of slavery in the new territory dominated congressional debate until the Civil War.
General Records of the U.S. Government, National Archives and Records Administration, Washington, D.C.
In Congress, one person may have reasons to keep information private, while another has equally compelling reasons to make it public. In 1844, as the volatile issue of slavery inflamed emotions, Senator Benjamin Tappan of Ohio gave a secret treaty to a journalist. He wanted to publicize sections of the treaty that would allow slavery in Texas.
The Senate censured Tappan and threatened to expel future members who "leaked," or revealed, secrets.
Four years later, someone in the Senate gave the still-secret Treaty of Guadalupe Hidalgo, ending the Mexican War, to New York Herald reporter John Nugent. Determined to make good on its threat to enforce secrecy, the Senate ordered Nugent imprisoned in the Capitol until he named his source. Nugent refused. A frustrated Senate eventually released the reporter without discovering his source.