Attorney General Ken Paxton also announced Backpage CEO Carl Ferrer has pleaded guilty to money laundering after a federal grand jury returned a 93-count indictment against his website.
The FBI seized Backpage.com on April 6, leaving nothing but a notice informing users of the website's seizure by the U.S. government.
An official with the U.S. Department of Justice told ABC News more than $500 million related to prostitution was laundered by the site using Bitcoin and other crypto-currencies.
The indictment included details about 17 victims of sex trafficking, some as young as 14 years old.
Backpage.com allowed users to create posts to sell items, seek roommates and post job openings. The site also had listings for adult escorts and other sexual services.
Authorities said advertising related to those services was "extremely lucrative."
On Oct. 6, 2016, the CEO of Backpage.com was arrested at Houston's Bush Intercontinental Airport after arriving on a flight from Amsterdam.
Ferrer was taken into custody following a joint investigation by the Texas and California attorneys general.
In December 2016, the state of California filed pimping and money laundering charges against Ferrer and former Backpage.com owners Mike Lacey and Jim Larkin.
Backpage.com removed the adult section from all of its websites last January after the U.S. Senate Permanent Subcommittee of Investigations released a report that accused the website of knowingly facilitating child sex trafficking.