The Senate censured Senator Benjamin Tappan (D-OH) for leaking to the New York Evening Post confidential documents associated with a treaty to annex the Republic of Texas. Originally, the Senate considered expelling Tappan, but his timely confession produced the lesser penalty of censure. The Senate then adopted a rule subjecting to expulsion any member "convicted of disclosing for publication . . . matter directed by the Senate to be held in confidence."

Factional divisions within the Senate Republican majority produced an extraordinary stalemate, beginning on this date, over the usually routine task of electing a Senate president pro tempore to preside in the absence of the vice president. A three-month deadlock resulted from Senate procedures requiring that such an election be decided by majority rather than plurality vote and prohibiting the body from conducting other business until the election was completed. Eventually, the exhausted members of both parties compromised with a plan to allow one Democrat and four Republicans to take turns presiding for the remainder of the congressional session.

The Constitution required that senators "shall be divided as equally as may be into three Classes . . . so that one-third may be chosen every second Year." In its first weeks of operation, the Senate established a committee to propose a method for implementing this requirement. On May 13, 1789, the committee offered a plan quickly adopted by the Senate. The twenty senators who were then serving arranged themselves into three nearly equally sized and geographically balanced classes, with no class containing two members from the same state. A senator representing each class drew from a box one of three papers numbered 1, 2, and 3. The class of the senator who drew #1 would serve until 1791, #2 until 1793, and #3 until 1795. As senators arrived from newly admitted states, they would draw lots for class assignment in a manner that would keep the classes balanced.

Although the Senate had employed pages as messengers since 1829, until this history-making day, all had been male. Taking their places at the head of what would become a long succession of female pages were Paulette Desell, sponsored by Senator Jacob Javits (R- NY), and Ellen McConnell, sponsored by Senator Charles Percy (R- IL).

On this date, the Senate began an investigation of two newspaper reporters for unauthorized publication in the New-York Tribune of an American treaty with Great Britain. This event occurred at a time when the Senate considered most treaties in closed session. When the reporters refused to reveal how they obtained this secret document, the Senate ordered them confined to a Capitol committee room. Enjoying the resulting notoriety, the correspondents feasted on meals sent in from the Senate dining room, entertained their wives and friends, and held the key to their "jail." After several days, the Senate gave up and released its prisoners.