The fitness event that happened first among the options provided is the opening of a YMCA gym in America. The first YMCA in the United States was established in Boston in 1851.
Here's a rough timeline for the other events:
- PE becomes part of the American school curriculum in the late 19th and early 20th centuries.
- Nautilus machines were introduced in the 1970s.
- Elliptical trainers gained popularity in the 1990s.
Therefore, the YMCA opening precedes the other events.