 Montessori traveled to the United States in December 1913 on a three-week lecture tour which included films of her European classrooms, meeting with large, enthusiastic crowds wherever she traveled.Montessori returned to the US in 1915, sponsored by the National Education Association, to demonstrate her work at the Panama–Pacific International Exposition in San Francisco, California, and to give a third international training course.A glass-walled classroom was installed at the Exposition, and thousands of observers came to see a class of 21 students.