During World War I, immigrants from Austria, Hungary, Germany and Ukraine were sent to Banff to work in internment camps. The main camp was located at Castle Mountain, and was moved to Cave and Basin during winter. Much early infrastructure and road construction was done by men of various Slavic origins although Ukrainians constituted a majority of those held in Banff. Historical plaques and a statue erected by the Ukrainian Canadian Civil Liberties Association commemorate those interned at Castle Mountain, and at Cave and Basin National Historic Site where an interpretive pavilion dealing with Canada's first national internment operations opened in September 2013.