Several forms of gambling are legal in the U.S. state of Massachusetts.
Parimutuel wagering on horse racing is allowed at the state's two active racetracks, Plainridge Racecourse and Suffolk Downs. Simulcast wagering on horse and dog races is also offered at Raynham Park, which previously operated as a dog racing track. 
Betting on horse and dog racing was legalized in 1934. 
The first dog tracks were Wonderland Greyhound Park and Taunton Dog Track, opened in 1935.   They were joined in 1941 by Raynham Greyhound Park.  The Taunton track closed in 1981,  and its operations were absorbed into the Raynham track, which became known as Raynham-Taunton Greyhound Park.  Both remaining tracks closed by the end of 2009, when dog racing was banned by the Massachusetts Greyhound Protection Act. 
Harness racing began in 1947 at Bay State Raceway (later named Foxboro Raceway).  Suffolk Downs included the sport in its calendar from 1959 to 1970.  Foxboro closed in 1997 and was replaced in 1999 with the opening of Plainridge. 
In addition to the major tracks, wagering was also conducted on horse and dog races at agricultural fairs around the state, including the Northampton Fair, Marshfield Fair, Great Barrington Fair, Weymouth Fair, Berkshire County Fair (at Berkshire Downs), Brockton Fair, and Topsfield Fair.   Race fixing was notoriously common at these meets.   This fair circuit came to an end when the last remaining venue, Northampton, held its final racing meet in 2005. 
Private lotteries were common in early colonial history, but as public attitudes turned against them, Massachusetts banned all lotteries in 1719.   The province's first public lottery was authorized in 1745, to pay for expenses related to King George's War.   At least fifteen lotteries were authorized from 1749 to 1761, until the Lords of Trade expressed their disapproval of the practice,  effectively banning public lotteries in Massachusetts until the American Revolution, when lotteries again became frequent, until a new ban was enacted in 1833.  The modern Lottery was created in 1971 and held its first drawings the following year. 
Eligible non-profit organizations are allowed to operate certain gambling games for fundraising purposes, including bridge and whist,  bingo (also called "beano"), raffles, pull tabs, and casino nights (referred to as "bazaars").  Senior citizen organizations ("golden age clubs") are also allowed to run bingo games with little oversight, with prizes of $100 or less. 
As of 2013, the total annual gross revenues reported for charitable gaming were about $66.5 million, with $33 million from bingo, $13 million from pull tabs, $20 million from raffles, and $400,000 from bazaars.  There were 157 licensed charitable bingo operators. 
Several poker rooms throughout the state operate under the casino night law, with daily games benefitting a rotating set of charities. 
Whist and bridge fundraisers were legalized in 1932.  Beano was legalized in 1934,  but then banned in 1943 because racketeers were operating games using charities as fronts.   Raffles and bazaars were authorized in 1969.   Beano was re-legalized in 1971, with a local election required in each city or town to allow it. 
Both of the state's federally recognized tribes have worked for several years to open gaming facilities on tribal lands, under the federal Indian Gaming Regulatory Act. The Mashpee Wampanoag Tribe hopes to open a casino on land in Taunton. The Wampanoag Tribe of Gay Head (Aquinnah) plans a small gaming facility in Aquinnah, on Martha's Vineyard.
The Mashpee tribe gained federal recognition in 2007. Their casino, referred to as Project First Light, would be located in what is currently an industrial park, which they have applied to the federal government to take into trust, making it sovereign tribal land. 
The Aquinnah tribe announced plans in 2013 for their Class II gaming facility in an unfinished community center on their reservation.  The state quickly sued to block the project, arguing that the tribe gave up gambling rights in a 1983 land settlement, in which the tribe agreed its lands would be subject to state law. The tribe argues that this agreement was superseded by the 1988 Indian Gaming Regulatory Act. 
Under the Expanded Gaming Act, passed in 2011, as many as three casino resorts and one slot parlor can be opened.  A slot parlor opened at Plainridge Park Casino in June 2015, and a casino resort, MGM Springfield, opened in 2018. Another casino resort, Encore Boston Harbor, is under development as of 2018 and scheduled to open in 2019. One more casino license may be issued for the southeastern part of the state, but the process has been delayed due to uncertainty about potential competition from the planned Mashpee Wampanoag casino. 
Gambling boats have operated at times out of Massachusetts harbors, taking passengers on "cruises to nowhere" in federal waters, where state gambling laws do not apply.  The first was the Vegas Express cruise, which sailed out of Gloucester from 1998 to 1999.   The Southern Elegance and the El Dorado set out from Gloucester starting in 1999,  as did the Midnight Gambler out of Lynn,  before it moved to Provincetown and operated for six weeks in 2000.  Another boat, run by Atlantic Casino Cruises, ran out of Gloucester from 2002 to 2003.   The Lynn harbor also played host to the Horizon's Edge casino cruise, from 2000 to 2009,   and the Aquasino, which ran for several months in 2013. 
- Gambling in the United States
- List of casinos in the United States
- Massachusetts Council on Compulsive Gambling
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