Source: microsite.smithsonianmag.com
Museum Day is an annual event hosted by Smithsonian Media in which participating museums across the country open their doors for free to anyone presenting a Museum Day Ticket.
Free museum admission* for 2 nationwide on Saturday – you have to register on the Smithsonian website first. (*at participating museums)
Here is the original post: Museum Day September 25th 2010 | Smithsonian.com
