Now, a tweet claiming "verbal government approval" is not official by any means, and it could just be the result of a garbled phone call between Musk and Trump.
While it's hard to imagine this enormous endeavor ever reaching fruition, Elon Musk has already achieved any number of things previously thought of as impossible.
Further more, some expressed concern over the actual possibility of even digging a tunnel under major cities in the first place.
The route - which would measure more than 200 miles (depending on where the start and end points were) would be built by Musk's Boring Company and would see journey times lasting just 29 minutes, according to Musk.
Musk said hyperloop tunnels could ferry people, cars and even bikes from NY to Washington in 29 minutes.
Musk also said today that another one of his ventures, The Boring Company, could aid in Mars colonization as well.
He made the announcement on Twitter, declaring his new super-fast transportation network will also have stops in Philadelphia and Baltimore, as well as "up to a dozen or more entry/exit elevators in each city".
Musk's plans for the East Coast were met with skepticism, especially in New York City, where commuters there are in the midst of the "summer of hell". The Boring Company did not immediately respond to a request for comment.
He attracted naysayers when he announced plans to build a reusable rocket - but his company SpaceX stunned the world in 2015 when it successfully guided a rocket to a safe landing after launch in a never-before-seen move.
One of those passions is the Hyperloop, a network of tubes that could carry passengers and cargo at near-supersonic speeds.
Musk has previously talked about building a tunnel system underneath Los Angeles to alleviate "soul destroying" traffic.
SpaceX plans to fly two paying customers to the moon late next year, using a Falcon Heavy.
"We're now getting comments from all the underground utilities and agencies who have live underground substructures" that could be impacted by the project, said Hawthorne's interim city manager, Arnie Shadbehr.