You can get onto the base to go to the Navy Museum, NFCU, or to visit someone who works/lives on the Navy Yard by going to Pass and ID at 11th St SE and O St SE. They will do a background check and give you a pass to get on base if you clear it.
This is an active Navy base, so you really need to normally have DoD base access already (DoD CAC or retiree ID card.) There is a way for others to get on base, but it's not easy. Just having an NFCU account is not enough and the branch is really just there for the people on the base.
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