With many states in the US changing their laws to allow the use of marijuana for recreational use, it was just a matter of time before hackathons for it were introduced. GrassRoots is a hackathon based in Seattle which aims to gather entrepreneurs, hackers, designers, and more on May 29-31 at the WeWork center to progress cannabis-related technology.

Undoubtedly it will be social apps which lead the pack, but there is a whole industry growing rapidly around its new legal status including; breathalyzers, delivery services, and real-estate market exchanges to take advantage of which investors are already putting serious money behind.

At a similar hackathon in Colorado last September called The Marijuana Tech Startup Competition, the eventual winner of the $2,500 cash prize was an app called CannaRegs. The app was built by Amanda Ostrovitz, a lawyer and a former bank examiner with the Federal Reserve, and acts as a regulatory service and a reference library for attorneys, consultants, compliance professionals and individual licensees.

The runner-up was 'CraftedHere' which "provides an online directory of cannabis-friendly bars, clubs and dispensaries for tourists and marijuana enthusiasts" to ensure they are heading to a safe and legal environment. Third place went to 'CannaBrokers' who "facilitates wholesale transactions between licensed growers, edibles producers and extract companies with dispensaries".

Daniel Starbuck is the lead developer at GrowBuddy, a service which helps growers monitor their cannabis crops to increase yield. He told BBC News he got into the industry after friends began growing medical marijuana: "I went into their grow house and saw that they had all these journals and notepads and everything, it was just a mess."

Most of the apps and services on offer help to provide guidance to both users and law enforcement in the early stages of its legality. It's not clear how many people are expected to attend GrassRoots, but the MassRoots event sold-out after expecting just 50 attendees. It goes to show how lucrative the so-called "Green Rush" looks set to be in the US states for entrepreneurs.

For more information on GrassRoots, head here.

Would you take part in a hackathon for cannabis-related technology? Let us know in the comments.