Was doing research on de-interlacing NTSC, as well as reading up on HDTV broadcasting. Ran accross this excellent description of how the ~59.94 hz field rate came to be. It was an artifact of retaining backwards compatibility with black and white TV's.

I didn't know that technically the field rate was dropped by a factor of 1000/1001.

Why NTSC has a ~59.94 hz field rate