The American is married to a New Zealander and spends about five months living in Wellington each year.
This year she ran the race again and finished it just under 25 minutes slower than she did half a century earlier.
"No woman has ever done that, but it's not a testimony to my greatness but because no women ran 50 years ago," Switzer said.
"Running has helped me cope with stress, gets me into a different space and feel fearless, and that's what I want to pass on to women everywhere."
Over the years, women have sent her photos of "261" written on their arms or their shirts when they have run their first race or when running for the first time.
"Who would have imagined that a race official would have attacked me in the race and tried to pull that bib number off, but I went on to finish" said Switzer.
"Today, 50 years later, 261 has become a number meaning fearless in the face of adversity."
Switzer recognised the strength behind the number and set up the charity where women can come together to run or learn to run in a non-judgmental, non-competitive environment.
"The global non-profit movement uses the sense of fearlessness that women get from running to go around the world and empower women through the simple act of putting one foot in front of the other."
The movement already has a following in Europe, the United States and Australia. Radio journalist and presenter Rachel Smalley will head the 261Fearless in New Zealand.
"Kathrine is the reason that we run, she was the one who brought around such change...when she asked me if I would help front it, I was absolutely 100 per cent on board," Smalley said.
"This is not about being thin, it's about being fit, it's about health and it doesn't matter what size or age or religion, 261 can help you."
Smalley was one of several Kiwi women from Auckland, Tauranga, Palmerston North and Christchurch who met and trained with Kathrine at Victoria Park in Auckland on Sunday.
The plan is to set up "pods" throughout cities in New Zealand.
"As you know, running has become a bit of a revolution in this country and it's mainly women who are taking to the roads, particularly if you look at the numbers running in the new events like the Queenstown Marathon and Hawke's Bay," Smalley added.