Sun May 25, 6:09 PM ET
Fourteen candidates ran for the nomination. Former Senator and Democratic presidential candidate Mike Gravel was defeated in the fourth round.
Third place finisher Wayne Allyn Root, an internet gambling entrepreneur, is the vice-presidential nominee.
Ruwart, a scientist and consultant from Texas, is a frequent Libertarian candidate, and challenged Republican Sen. Kay Bailey Hutchison in 2000. She campaigned earlier this year for Rep. Ron Paul, R-Texas, who is running for Republican presidential nomination. He also espouses libertarian beliefs.
"I'm sure will we emerge here with the strongest ticket in the history of the Libertarian Party," Barr said in his victory speech.
"This team, this candidate, will not let you down. This will be an historic and positive campaign that will succeed," he added.
Barr, 59, left the GOP in 2006. He is perhaps best known as a key player in the impeachment proceedings against President Bill Clinton.
Some of his earlier positions were at odds with the party. He was an opponent of the legalization of medical marijuana, a position he has since reversed. The Libertarian party's platform states that "all laws establishing criminal or civil penalties for the use of drugs" should be repealed. And he was a strong opponent of abortion rights. The party opposes any restrictions on reproductive rights.
But he was always a gun rights supporter, and called for the end to federal income tax and the IRS, all Libertarian principles.
"Bob Barr is one of the strongest candidates in the Party's 37-year history, and we look for him to have an enormous impact in the 2008 race," Libertarian Party spokesperson Andrew Davis said.
The final vote was 324 for Barr to 276 for Ruwart and 26 for "none of the above."
The Libertarian Party is on the ballot in 28 states.
Copyright © 2008 Congressional Quarterly Inc.