Over Larson's lifetime, she acquired 1,400 pieces of fashion spanning 400 years, from the 1600s to the 1950s.
It is remarkable since Larson started out simply as a homemaker with a passion for fashion.
When she died, the collection came to FIDM, which is now facing a December deadline to raise $2 million to acquire it.
The fundraising starts now -- or the collection is likely broken up and sold off for a lot more.
FIDM displays the pieces in rotating exhibits: Everything from Queen Victoria's gown to brocade shoes and matching hose to a Coco Chanel 1925 couture piece that still looks modern.
PHOTOS: Rare clothing collection on display at FIDM
For the students, it is a priceless living textbook about the best of the best, a source for academic inspiration. For the rest of us, it's just awe inspiring.
The fundraising is happening on social media with a hashtag #4for400 -- a very modern approach to save irreplaceable history.
A $4 donation can help save 400 years of fashion history -- if a half-million people donate.
To donate, visit http://www.fidmmuseum.org/support/donate-online/.