Oklahoma holds eleven public regional universities, including Northeastern State University, the second-oldest institution of higher education west of the Mississippi River, also containing the only College of Optometry in Oklahoma and the largest enrollment of Native American students in the nation by percentage and amount. Langston University is Oklahoma's only historically black college. Six of the state's universities were placed in the Princeton Review's list of best 122 regional colleges in 2007, and three made the list of top colleges for best value. The state has 55 post-secondary technical institutions operated by Oklahoma's CareerTech program for training in specific fields of industry or trade.