Over 50 Massachusetts museums will open their doors for free on Saturday, Sept. 21, thanks to Smithsonian Magazine and its 15th annual Museum Day. For this one-day event, museums and cultural institutions all across the country will offer free admission to anyone with a Museum Day ticket. 

Here’s what you need to do: visit smithsonianmag.com/museumday and search for the participating institution you’d like to visit. Then download your ticket, which grants free general admission for two people. 

Museums in all 50 states have signed up to participate in this year’s event, and more than 1,300 museums are expected to join in. 

Participating Massachusetts museums:

Armenian Museum of America - Watertown  Atwood Museum - Home of the Chatham Historical Society - Chatham  Beneski Museum of Natural History - Amherst  Cahoon Museum of American Art - Cotuit  Cape Cod Maritime Museum - Hyannis  Charles River Museum of Industry and Innovation - Waltham Cogswell's Grant - Essex  Cooper-Frost-Austin House - Cambridge  Davis Museum at Wellesley College - Wellesley  Discovery Museum - Acton  Durant-Kenrick House & Grounds - Newton  EcoTarium - Worcester  Edward M. Kennedy Institute for the United States Senate - Boston  Egan Maritime's Nantucket Shipwreck & Lifesaving Museum - Nantucket  Eustis Estate - Milton  Falmouth Museums on the Green - Falmouth  Fitchburg Art Museum - Fitchburg  Fruitlands Museum - Harvard  Gibson House Museum - Boston  Harvard Art Museums - Cambridge  Harvard Museum of Natural History - Cambridge  Jackson Homestead and Museum - Newton  John Cabot House - Beverly  John F. Kennedy Museum - Hyannis  John F. Kennedy National Historic Site - Brookline  Marblehead Museum - Marblehead  Marconi - RCA Wireless Museum - North Chatham  Mattapoisett Museum - Mattapoisett  Mead Art Museum - Amherst  Merwin House - Stockbridge  Museum of Family Prayer - North Easton  Museum of Fine Arts Boston - Boston  Museum of Printing - Haverhill  Museum of Russian Icons - Clinton  Native Plant Trust - Framingham  New Bedford Whaling Museum - New Bedford  Old Colony History Museum - Taunton  Peabody Museum of Archaeology and Ethnology - Cambridge   Quincy Homestead - Quincy  Roch-Jones-Duff House & Garden Museum - New Bedford  Sandwich Glass Museum - Sandwich  Spellman Museum of Stamps & Postal History - Weston  Springfield Museums - Springfield  Susan B. Anthony Birthplace Museum - Adams  The Eric Carle Museum - Amherst  The Gardner Museum - Gardner  The Mary Baker Eddy Library - Boston  The Paul S. Russell MD Museum of Medical History & Innovation - Boston  USS Constitution Museum - Charlestown  Wenham Museum - Wenham  William Hickling Prescott House - Boston  Worcester Art Museum - Worcester  Worcester Historical Museum - Worcester  Yiddish Book Center - Amherst