April 18 – New York City Parks Commissioner Robert Aaron proposes a new 78-acre (320,000 m2) tract in Flushing Meadows as a site for a new National League baseball stadium. The plan, submitted to mayor Robert Wagner, includes a 50,000-seat stadium with a plastic dome to be built by the Parks Department.
April 21 – In the first inning of a 3-1 loss to the Milwaukee Braves at Milwaukee County Stadium, the Cincinnati Redlegs are involved in a bizarre play. With Don Hoak on second and Gus Bell on first, Wally Post hits a ground ball to Milwaukee shortstop Johnny Logan. Hoak breaks up a potential double play by fielding the ball himself and flipping it to Logan. Hoak is called out for interference (contact with a batted ball before a fielder touched it), but Post is given a single on the play. The day before, Johnny Temple let Bell's ground ball hit him with the same result, Temple being called out for interference and Bell being awarded a single. The two incidents prompt league presidents Warren Giles and Will Harridge to jointly announce a rule change that declared both the runner and batter out if the runner intentionally interfered with a batted ball, with no runners allowed to advance.
May 7 – Two batters into the game at Cleveland Stadium, Cleveland Indian pitcher Herb Score is hit in the face by a line drive by New York YankeeGil McDougald, the ball breaking numerous bones in Score's face and leaving him quite bloodied. McDougald vows to quit if Score is blinded as a result. Score regains his 20/20 vision, but will miss the remainder of the 1957 season. With Bob Lemon pitching the rest of the way, the Indians defeat the Yankees 2-1.
July 18 – Stoneham says the Giants will quit New York after the season. He says he has not heard anything more from San Francisco and that his move is not contingent on that of the Dodgers. He sees a new stadium or joint occupancy with the New York Yankees as the only reason for the Giants to stay in New York.
August 19 – As Stoneham cites poor attendance as the reason for the Giants' move, the team's board of directors votes 8-1 to move to California in 1958, as San Francisco promises a new stadium in the Bayview area. The only dissenting vote is by M. Donald Grant, who would go on to be one of the founders of the New York Mets.
November 20 – Shigeo Nagashima, a slugger star at Rikkyo University, signs with the Yomiuri Giants for a record bonus of $69,000. He will go on to have one of the great careers in Nippon Pro Baseball.
In a controversial vote, Mickey Mantle barely edges Ted Williams, 233 to 209, to win the American League MVP Award. Mantle batted .365 with 34 home runs for the first-place New York Yankees, while Williams, of the third-place Boston Red Sox, led the AL with a .388 average and 38 home runs, as well as a stunning .731 slugging percentage. Red Sox owner Tom Yawkey fumes at the news, noting that two Chicago writers listed Williams in the ninth and tenth places on their ballots.
After 22 seasons of work, Larry Goetz is unwillingly 'retired' as a National League umpire by league's president Warren Giles. The discharged arbitrator had been critical of the Senior Circuit because of the league's refusal to include umpires in the players' pension fund.
November 26 – Yoshio Tanaka, an American citizen of Japanese descent, is named manager of the Hanshin Tigers. Tanaka is the first American to manage a Japanese ML team.
November 28 – Milwaukee Braves pitcher Warren Spahn, who posted a 21-11 record with 111 strikeouts and a 3.49 ERA, wins the MLB Cy Young Award almost unanimously. His only competition for the title is Dick Donovan of the Chicago White Sox (16-6, 88, 3.35), who receives one vote. Only one pitcher is selected each season for this prestigious pitching award until 1967, when each league will name a winner.
January 31 – Chick Maynard, 60, shortstop for the 1922 Boston Red Sox
March 2 – Frank Hafner, 89, pitched two games for the 1888 Kansas City Cowboys of the American Association.
April 15 – Jack Coombs, 74, pitcher with 158 career victories including a 31-9 campaign for the 1910 Athletics; pitched a complete 24-inning game on September 1, 1906, winning 4-1; later the baseball coach at Duke University from 1929 to 1952