Atlantic League of Professional Baseball

The Atlantic League of Professional Baseball is a professional, independent baseball league located primarily in the Mid-Atlantic and Northeastern United States, especially the greater metropolitan areas of the Northeast megalopolis, with one team located in Texas. League offices are located in Lancaster, Pennsylvania.

The Atlantic League operates in cities not served by Major League Baseball (MLB) or Minor League Baseball (MiLB) teams and is not affiliated with either; most of its teams are within suburbs and exurbs too close to other teams in the organized baseball system to have minor league franchises of their own. The Atlantic League requires cities to have the market for a 4,000 to 7,500-seat ballpark and for the facility to be maintained at or above Triple-A standards. When Atlantic League professionals are signed by MLB clubs, they usually start in their Double-A or Triple-A affiliates. The league uses a pitch clock and limits the time between innings in an effort to speed up the game. In 2019, the Atlantic League began a three-year partnership with Major League Baseball allowing MLB to implement changes to Atlantic League playing rules, in order to observe the effects of potential future rule changes and equipment.

History
In 1998, the Atlantic League of Professional Baseball played its inaugural season, with teams in Bridgewater, Newark, and Atlantic City, New Jersey; Nashua, New Hampshire; Newburgh, New York; and Bridgeport, Connecticut. The creation of the league was the result of the New York Mets' objection to Frank Boulton's proposal to move the former Albany-Colonie Yankees because of its territorial rights to the region. Boulton, a Long Island native, decided to create a new league that would have a higher salary cap for its players and a longer season than most of the other independent baseball organizations. He modeled the Atlantic League after the older Pacific Coast League, with facilities that exceed AAA-level standards. Boulton also emphasized signing players of Major League Baseball experience for all Atlantic League teams, raising the level of play above other independent leagues.

In 2010, the league announced that it would be expanding to Sugar Land, Texas and adding its first franchise not located in an Atlantic coast state. The Sugar Land Skeeters began play in 2012. In 2010, amid financial struggles, the Newark Bears moved from the Atlantic League to the Can-Am League, leaving the Bridgeport Bluefish and Somerset Patriots as the only teams remaining from the league's inaugural season. In the summer of 2013, then-ALPB President Frank Boulton announced that he would be resigning so that he could devote more time to operating the Long Island Ducks. He was replaced by longtime high-ranking Major League Baseball executive Rick White. On July 8, 2015, the Atlantic League began using Rawlings baseballs with red and blue seams, virtually unused in the sport since the American League swapped the blue in their seams for red in 1934.

On September 1, 2015, the Atlantic League announced conditional approval for an expansion team or a relocated team to play in New Britain, Connecticut for the 2016 season. On October 21, 2015, the Camden Riversharks announced they would cease operations immediately due to the inability to reach an agreement on lease terms with the owner of Campbell's Field, the Camden County Improvement Authority. The team was replaced by the New Britain Bees for the 2016 season. On May 29, 2016, Jennie Finch was the guest manager for the league's Bridgeport Bluefish, thus becoming the first woman to manage a professional baseball team.

Shortly before the conclusion of the 2017 season, the city of Bridgeport, Connecticut voted to not continue with professional baseball in the city and announced plans to convert The Ballpark at Harbor Yard into a music amphitheater; the Bridgeport Bluefish announced plans to relocate to High Point, North Carolina in 2019 when the construction of a new multipurpose facility in High Point is completed. League officials announced the return of the Pennsylvania Road Warriors, an all road game team, to keep the league at an even eight teams while the Bluefish go inactive for the 2018 season.

The Atlantic League is generally regarded as the most successful and highest level of baseball among independent leagues. Two former Atlantic League players have been inducted into the Baseball Hall of Fame: Tim Raines and Rickey Henderson. Other notable former and future Major League ballplayers who have played in the league include Roger Clemens, Scott Kazmir, Dontrelle Willis, Juan González, Rich Hill, John Rocker and José Canseco, and several others have coached or managed, including Gary Carter, Tommy John, Bud Harrelson, Gary Gaetti and Sparky Lyle. The Atlantic League has consistently posted higher per game and per season attendance numbers than other independent circuits including the American Association, Can-Am League, and Frontier League.

In 2015, the Atlantic League experienced a watershed moment for independent baseball when it signed a formal agreement with Major League Baseball which put into writing the rules which the ALPB would follow in selling its players' contracts to MLB clubs and their affiliates. This marked the first time that MLB, which has enjoyed a U.S. Supreme Court-granted antitrust exemption since 1922, had made any formal agreement with or acknowledgment of an independent baseball league.

2019 experimental rules
In March 2019, the Atlantic League and Major League Baseball reached agreement to test multiple rule changes during the 2019 Atlantic League season:
 * Use of a radar tracking system to assist umpires in calling balls and strikes
 * Reducing the time between half innings by 20 seconds, from 2 minutes 5 seconds to 1:45
 * Requiring pitchers to face at least three batters
 * Exceptions: side is retired, or injury
 * Banning mound visits
 * Exceptions: pitching change, or for medical issues
 * Restricting infield shifts
 * Two infielders must be positioned on each side of second base
 * Increasing the size of bases from 15 in to 18 in
 * The size of home plate is not altered
 * Moving the pitching rubber on the pitcher's mound back 24 in
 * This change would have taken effect in the second half of the season

In April 2019, implementation of two of the changes was delayed:
 * The tracking system for calling balls and strikes "will be implemented gradually over the course of the 2019 season"
 * Moving the pitching rubber back will not occur until the second half of the 2020 Atlantic League season

The tracking system for calling balls and strikes was introduced at the league's all-star game on July 10. In addition to rule changes noted above, additional changes being implemented for the second half of the league's 2019 season are:
 * Pitchers required to step off rubber to attempt pickoff
 * One foul bunt permitted with two strikes
 * Batters may "steal" first base
 * "Any pitched ball not caught by the catcher shall be subject to the same baserunning rules for the batter as an uncaught third strike, with the exception of the first base occupied with less than two out exclusion."
 * "Check swings" more batter-friendly
 * "In making his ruling, the base umpire should determine whether the batter’s wrists 'rolled over' during an attempt to strike at the ball and, if not, call the pitch a ball."

League timeline
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Championship series
The championship series is played as a best-of-five. Numbers in parenthesis denote the number of championships won by a team to that point, when more than one.

All-Star games
† Freedom Division won the 2019 game in a "homer-off" after the teams were tied at the end of nine innings.