Alongside the presidential election last week, sports betting was approved by voters of three US states last week: Maryland, Louisiana and South Dakota.

This means that two and a half years after the US supreme court opened the doors to legal wagering, 20 US states have so far taken up the option, plus this new trio that should all go live next year, and almost another 20 publicly mulling it over.

It’s not surprising that this has been seen as the next gold rush for a group of companies that has existing technology, several of which are listed in London.

With one of those, William Hill PLC (LON:WMH) in the process of being taken over by its US casino partner, Caesars Entertainment Inc (NASDAQ:CZR), and Flutter Entertainment PLC (LON:FLTR) this week flagging its expectation of being the first provider to top US$1bn of gross gaming revenue, investors are still likely to find good odds out there.

US punters can currently bet online on horse racing, basketball, gridiron, ice hockey and a varying number of other options in a total of 20 states, with several having opened up in 2020: Illinois, Michigan and Montana went live in March, followed by Virginia in April, Colorado in May, Washington DC in June and Tennessee in November.

This month’s election saw voters approve betting in-person and online in Maryland, across most of Louisiana and small parts of South Dakota, while three other states voted to widen existing laws.

Nebraska voted to add casinos at its racetracks and legalise “all games of chance”, which turns the decision over to local lawmakers to decide whether this includes sports betting; Virginia approved casinos in four cities; and wagering limits were raised for Colorado’s three tribal reservation casinos.

Tribal casinos in some other states, such as Oklahoma, are likely to be the location for sports betting hubs, while various sports betting legislative activity has taken place in 19 other states without a near conclusion in sight: Alabama, Alaska, Arizona, California, Connecticut, Florida, Georgia, Hawaii, Kansas, Kentucky, Massachusetts, Minnesota, Missouri, Ohio, South Carolina, Texas, Vermont and Wyoming.

Currently, the likes of Flutter’s FanDuel, GVC Holdings PLC’s (LON:GVC) BetMGM partnership with the casino group, and William Hill’s Caesars venture are live around half the available states, leaving plenty of room for growth.

More precisely, FanDuel was live in seven states in the third quarter and having gone live in Tennessee and with Michigan and Virginia in coming months will soon be up to 10, with Flutter its US businesses are on track to make an EBITDA loss of £160-180mln this year. Flutter says it has a 46% market share of GGR in sports betting and 22% in gaming.

Over at GVC, the BetMGM joint venture is providing sports betting and i-gaming in eight states and expects to be up to 11 by the end of the year, recently said net revenues in the US are expected to approximately US$150-160m

William Hill said last month it was live in 14 states, having opened in Colorado, Illinois, Michigan and Washington DC during the third quarter and since added Pennsylvania.

Online casino specialist 888 Holdings (LON:888), which has a longstanding consumer-facing and white-label B2B business in the US but has been questioned about the lack of a heavyweight partner, grew US revenue 90% in the first half of this year, thanks to B2C growth in New Jersey as well as strong performances from B2B partners.

By 2025, the US market is forecast to be generating US$18bn of gross revenue and US$4.3bn of EBITDA, according to calculations by broker Peel Hunt, while analysts at Jefferies a US$5bn EBITDA opportunity from online gambling with internet gaming potentially doubling that market size.

With Caesars bid for William Hill coming hot on the heels of US investment vehicle InterActiveCorp (NASDAQ:IAC) spending U$1bn to snap up a 12% stake in MGM, many investors are already betting that more M&A is around the corner.