The 1857 baseball convention was a meeting of members from 16 New York City-area baseball clubs that took place over multiple sessions in early 1857. It passed numerous clarifications of the pre-existing Knickerbocker Rules and modifications that helped lead to the modern format of baseball games. Among the items formalized were the length of games and the distance between bases.
At the convention, multiple members of the New York Knickerbockers club presented the "Laws of Base Ball", a series of documents that contained proposed rules, some of which were edited in response to feedback. The law documents drafted for the convention survived and were sold at auction for more than $3 million in 2015.