Buchanan was Director General of the Pan-American Exposition, held in Buffalo, New York from May 1 through November 2, 1901, and is credited with the construction, operation, and dismantling of the exposition. He was chosen by John G. Milburn, president of the exposition, as the exposition was planned with a Latin American theme and they wanted someone who knew the South American countries well. President McKinley was assassinated at the exposition by anarchist Leon Czolgosz on September 6, 1901, and Roosevelt traveled to Buffalo where he was inaugurated shortly thereafter.