COWLITZ INDIAN RESERVATION — Ilani Casino Resort opened its new event center Thursday, bringing more demand and attention to northern Clark County.The 30,000-square-foot center allows Ilani to host concerts, trade shows, corporate meetings and other high-traffic events. It will offer the biggest ballroom in the county, and it is already the largest gaming complex near the Vancouver-Portland metropolitan area.The space’s biggest footprint belongs to a 22,000-square-foot banquet hall that can seat 800 people at tables or serve a standing audience of 2,500. It can be partitioned for other uses, and there are separate conference rooms as well.The venue’s first headliners have already been announced, but the official ribbon-cutting was Thursday morning. It started in the rain outside before crowds of local officials, casino staff and members of the Cowlitz Indian Tribe swarmed indoors and around Ilani’s sprawling gaming floor.Tribal officials said that after nearly two decades of planning and legal battles to build the casino — along Interstate 5 west of La Center at Exit 16 — they now have plenty of momentum. The new venue opens less than a year after the casino, noted Cowlitz Tribe Chairman Bill Iyall.