A man from Austin is accused of being the mastermind behind an online black market for drugs.
FBI officials say Ross Ulbricht ran the site that generated more than $1 billion in sales.
Ulbricht was arrested Tuesday at a San Francisco library.
The 29-year-old, known online as Dread Pirate Roberts, is charged with conspiracy to traffic narcotics, hacking and money laundering.
He is also charged in federal court in Baltimore with soliciting the murder of a witness from an undercover agent. Ulbricht is accused of asking the agent to kill a former employee for $80,000, according to the affidavit.
Ulbricht didn't enter a plea to any of the charges when he appeared in court Wednesday in San Francisco. He is due back in San Francisco federal court on Friday to discuss bail and his transfer to New York, where most of the charges have been filed.
The Associated Press contributed to this report.