John Ten Eyck Lansing Jr. (January 30, 1754 – vanished December 12, 1829), a Founding Father of the United States, was an attorney, jurist, and politician.

[1][2] Born and raised in Albany, New York, Lansing was trained as a lawyer, and was long involved in politics and government.

In 1790, Lansing was a member of the commission that settled the New York-Vermont boundary as part of Vermont's admission to the Union as the fourteenth state in 1791.

Lansing's desire was to see the Articles strengthened by giving it a source of revenue, the power to regulate commerce, and to enforce treaties.

[7] Lansing, along with fellow New York delegate Yates, as well as Luther Martin of Maryland and George Mason of Virginia, strongly opposed the newly proposed United States Constitution because they thought it was fundamentally flawed and it infringed on the sovereignty of the independent States while not doing enough to guarantee individual liberty.

[8] Both Lansing and Yates walked out of the convention after six weeks and explained their departure in a joint letter to New York Governor George Clinton.

At the New York Ratifying Convention that followed, Lansing, along with Melancton Smith, took the lead in the debates as the leaders of the Anti-Federalist majority.

[10] On the evening of December 12, 1829, Lansing left his Manhattan hotel to mail a letter at a dock in New York City, never to be seen again.

Lansing's fate was a major mystery in New York State at the time, rivaled only by the 1826 disappearance of William Morgan, the anti-Masonic writer.

Weed said they were all dead by 1870, but he did not wish to harm their respected family reputations, so upon advice of two friends he decided not to reveal what he had been told.