Closet metro station to National Air and Space Museum, DC?

Adam is correct that L'Enfant Plaza is a bit closer, but I generally recommend the Smithsonian station. When you come out of the Smithsonian station, you're right on the Mall, and you have an easy walk to the Air & Space. Just take the exit marked "National Mall", go up the escalator, look for the US Capitol, and start walking in that direction. In about 5-10 minutes you'll be at the Air & Space. The L'Enfant Plaza station is a bit more confusing for tourists to use, and when you come to street level it can take a bit of effort to orient yourself.

L'Enfant Plaza is the closest station to the Air and Space Museum, and is also on the orange line.

The Smithsonian one is pretty close, but not sure if its the closest...

Definitely select the Smithsonian Station. So easy and, aside from closures for security reasons, this is a pretty stable Metro station. L'Enfant seems to be constantly suffering from escalator problems.

L'Enfant is actually a bit closer. I avoid Smithsonian station because of all the stroller people there, and it gets crowded. Both stations are on the Orange Line.

I've been to regular metro stations, but I have not stumbled upon a closet one. What is it? Really small?