I have been to most of the Smithsonian museums, and they have all been great, It just depends on what your interests are. As far as handicap accessibility and parking, I suggest you call the museums directly after she makes up her mind about which ones to see, and find out what they advise. Many people take the Metro to the Smithsonian Station, but I don't know how close that is to what she may want to see. If your sister had a wheelchair with her -- perhaps a rental? -- if would make things much easier.

I would try for a rental on a mobility chair. They are so great when you need one.

Parking for any of them is pretty much hit and miss and I' ve never found any very close. Can she do a bus? There are plenty of sightseeing buses that could get you fairly close. I did not know the museums provided wheelchairs....learn something new every day.

Here's a link that might help:
http://www.mnh.si.edu/visit/accessibility.htm

Mall parking is very limited especially in the spring and summer which is prime tourist season. DC does have free handicap parking at "red top" meters but you can't count on that. Be sure that you locate the handicap entrances also because almost all the bldgs. have steps to enter.

My husband is disabled with MS and can't walk. He has a wheelchair for around the house. We also bought a "Transport chair" for about $200 from a local big-box pharmacy. It's essentially a light-weight wheelchair with 4 small wheels that folds up. It can be easily folded to fit in a car or bus. It has no motor or "big wheels" for the rider to use, but it can support up to 250 pounds. I push him in it.

As far as museums go, I have always loved the Museum of Natural History the best. It has such a wide variety of things to look at.
As far as accessability, I believe you can drive pretty close to the entrance to drop someone off. Then the driver can go for a parking space. We did this with my mother some years ago. Plan on her waiting about 30 minutes after she gets dropped. It can be a long walk back.

All the Smithsonian museums are worth the time to visit. If it can be arranged, a tour of the Capitol and White House would be wonderful. There's so much to see in D.C., and I would definitely recommend a wheelchair rental.

My guess would be that the Metro would be easier than trying to deal with traffic and parking a car.

I think with some pre-planning, it will be a fantastic trip! There is SO much to see and do.

I would vote for the American History Museum! And the National Zoo...

We went to DC last year. My brother and his wife drove down from New Jersey. SIL had broken her foot. She rented a wheelchair from back home. Db pushed her around. Our hotel was in MD so we just rode the Metro and used the handicap access.

Visiting the Smithsonians is very time consuming. We only did a couple. The American History Museum was our fav. We also saw the Air and Space museum. I don't think you could probably go wrong with any of them. It all depends on your interests.

My sister was along on the trip also. She went to the zoo. It was in the 90's. Dsis said many of the animals were not out and walking around because of the heat.

Thanks everyone! I think they will rent a wheelchair; I hope they can find one like Jannie mentioned. I am leaning toward recommending the Natural History one. I was there almost 30 years ago and could have stayed all day.

Don't bother with White House visits anymore. Not done IN the White House. The zoo is pretty far out from the center of things. I agree with either the Natural History one or the American History one. I would avoid Capitol Hll this week with the protests about heathcare going on at the Supreme Court which is on that same hill. Printing and Engraving is also good as is the Natioal Archives, but the archives ALWAYS have a long wait for tickets. Fortunateley, I live only a $4 train ride away. (An hour by car)

About what Salgal says: On Madison Drive (this is one of the streets that borders the National Mall and the Smithsonian museums), you CAN pull a car up very close to the Natural History museum, but if your sister can't walk up the big stone staircase there, if she will need a wheelchair right away, she and her friend need to instead use the Constitution Avenue entrance, in the back of the building. (Pretty sure, if my mind's-eye is picturing it accurately, that there are also some steps that lead into the American History museum, but not as many as at Natural History.)

I think the Natural History website says they will lend you wheelchairs inside the museum, but you can't take them out -- this makes me think not even to immediately sit someone you have dropped off in front.

It might be that Constitution Avenue is the main access point for the handicapped to all the Smithsonian museums on that side of the National Mall.

If she can use the Metrorail public-transit system, the Smithsonian Station can be walkable to the American History and Natural History museums. But sometimes elevators are out of service at Metro stations (there's a big maintenance problem across the Metro system, and there are frequent service interruptions cuz workers are trying to clear the backlog).

I think it all depends on how much she can walk before she needs the wheelchair.

Also, this info may make you think that it's gonna be such a struggle to get around, but just a few phone calls to the museums can get you some advice as to the shortest, best route for your sister from Point A to Point B.

(PS: Natural History is cool, National Gallery of Art, Air & Space, but American History is a little more general interest and more fun, in my opinion.)

Best part of the Smithsonian Museums, they are all free, no admission charges. Been there several times, a wonderful experience.