The 80th New York State Legislature, consisting of the New York State Senate and the New York State Assembly, met from January 6 to April 18, 1857, during the first year of John A. King's governorship, in Albany.
 Under the provisions of the New York Constitution of 1846, 32 Senators were elected in single-seat senatorial districts for a two-year term, the whole Senate being renewed biennially. The senatorial districts (except those in New York City) were made up of entire counties. 128 Assemblymen were elected in single-seat districts to a one-year term, the whole Assembly being renewed annually. 
 The Assembly districts were made up of entire towns, or city wards, forming a contiguous area, all in the same county. The City and County of New York was divided into four senatorial districts, and 16 Assembly districts.
 At this time there were two major political parties: the Democratic Party and the Republican Party. The Know Nothing movement ran in the election as the "American Party."
 The New York state election, 1856 was held on November 4. Republicans John A. King and Henry R. Selden were elected Governor and Lieutenant Governor. The other three statewide elective offices were also carried by the Republicans. The approximate party strength at this election, as expressed by the vote on Governor was: Republican 265,000; Democratic 198,000; and American 130,000.
 The Legislature met for the regular session at the Old State Capitol in Albany on January 6, 1857; and adjourned on April 18.
 DeWitt C. Littlejohn (R) was again elected Speaker with 79 votes against 35 for David R. Floyd-Jones (D), and 7 for Joseph B. Varnum Jr. (A). William Richardson (R) was elected Clerk of the Assembly with 78 votes against 37 for John S. Nafew (D) and 7 for G. M. Stevens (A).
 On January 24, Mark Spencer (D) was elected president pro tempore of the State Senate.
 On February 3, the Legislature elected Preston King (R) to succeed Hamilton Fish as U.S. Senator from New York for a six-year term beginning on March 4, 1857.
 On April 7, the Legislature elected Henry H. Van Dyck (R) to succeed Victor M. Rice as State Superintendent of Public Instruction.
 On April 13, the Legislature re-apportioned the Senate districts, and the Assembly seats per county. Cayuga, Dutchess, Genesee, Greene, Montgomery, Onondaga, Orange, Otsego, Schoharie and Tompkins counties lost one seat each; New York, Oswego, Queens, Ulster and Westchester counties gained one seat each; Kings County gained four seats; and the new Schuyler County was apportioned one seat.
 On April 15, the Legislature passed "An Act to establish a Metropolitan Police District, and to provide for the government thereof." This act re-organized, and unified, the police forces in New York City, Staten Island, Kings County and Westchester County. The Metropolitan Police was headed by a Board consisting of five Commissioners (appointed by the Governor, and confirmed by the Senate) and the Mayors of New York City and Brooklyn. At first, Mayor Fernando Wood did not recognize the Metropoplitan Police, and refused to disband the Municipal Police. The struggle led to the New York City Police Riot, but after the New York Court of Appeals upheld the Legislature's police law, Mayor Wood quietly agreed to abide by it.
 The asterisk (*) denotes members of the previous Legislature who continued in office as members of this Legislature.
 Party affiliations follow the vote on U.S. Senator and Regent of the University.
 The asterisk (*) denotes members of the previous Legislature who continued as members of this Legislature. Richard U. Sherman, the Clerk of the Assembly during the previous Session, was elected a member.
 Party affiliations follow the vote for Speaker.