Gaming Group, and announced that the 2005 Series events would be held at the Harrah's-owned Rio Hotel and Casino, located just off the Las Vegas Strip. Since 2004 the official sponsor of the World Series of Poker has been the Caesars Entertainment Corporation. The final two days of the 2005 WSOP Main Event were held downtown at what is now the MTR-operated "Binion's" in celebration of the centennial of the founding of Las Vegas. The WSOP added a made-for-television $2 million "freeroll" invitational Tournament of Champions (TOC) event first won by Annie Duke as a "winner-take-all" event. 2005 expansion – WSOP Circuit Starting in 2005, the WSOP began the World Series of Poker Circuit, a satellite series held at Harrah's-owned properties in the United States. In addition to the $10,000 buy-in tournament at each site, qualifying players became eligible for a revamped Tournament of Champions. The 2005 TOC, made up of the top twenty qualifying players at each circuit event, along with the final table from the 2005 Main Event and the winners of nine or more bracelets (Johnny Chan, Doyle Brunson, and Phil Hellmuth) would participate in the revamped TOC at Caesars Palace. Mike Matusow won the first prize of $1 million (US), and all the players at the final table were guaranteed a minimum of $25,000 for the eighth and ninth-place finishers. During a break in the final table of the 2005 Main Event on July 16, Harrah's announced that eleven properties — including the recently added Bally's and Caesar's properties — would host 2005–06 WSOP Circuit events that started on August 11 in Tunica, Mississippi. One event that was scheduled for Biloxi, Mississippi, was canceled after the Grand Casino Biloxi, which was scheduled to host the event, suffered major damage from Hurricane Katrina. The Rio also hosted the 2006 World Series of Poker, which began on June 25 with satellite events and formally began the day after with the annual Casino Employee event, won in 2006 by Chris Gros. 2006 featured the Tournament of Champions on June 25 and 26, won by Mike Sexton. Various events led up to the Main Event, which was held from July 28 until August 10. The first prize of $12 million was awarded to Jamie Gold. 2007 expansion – WSOP Europe The World Series of Poker Europe (WSOPE) is the first expansion of the World Series of Poker in series history.