The SS United States, built more than 70 years ago, is being towed from Philadelphia to Mobile, Alabama, to become the world's largest artificial reef.

The SS United States completed a major step towards becoming the largest artificial reef in the world as the ship arrived in Mobile, Alabama on Monday, completing an 1,800-nautical mile journey from Philadelphia.

The SS United States completed its long trip from Philadelphia to the Port City on Monday, but in many ways, its journey is just beginning.

Crews will spend about six months cleaning the 1,000-foot vessel and removing hazardous materials as they prepare it to eventually be sunk off Florida's Gulf coast.

The historic, aging ocean liner that a Florida county plans to turn into the world’s largest artificial reef has completed the first leg of its final voyage.