When I lived in the DC area years ago, my friends and I would go to the Mall to watch the fireworks on 4th of July. It was always hot and sweaty and crowded but I always felt safe.  

Yes,....about a million people still pack the Mall in DC to watch the fireworks.  If you like crowds, it is plenty of fun and definitely safe (except perhaps pickpockets).  Bring a blanket and enjoy.  I don't think they allow coolers still.  They usually have a concert before.  However, if you are "young, female, and beautiful", you can likely get invited to one of the many office rooftops which is much more relaxed, often with open bars and AC available when you get hot.  Also, if you can find someone with boat, that is also a great place to partake.  My only real advice is to make dinner reservations or some other plans for after the fireworks.  Otherwise, you are sitting in your car (or on Metro) for over an hour.

We quit going to the Mall after 9/11.  Everything changed and frankly it isn't that much fun anymore.  Controlled access and metal detectors just aren't my thing.  As far as being safe, it is probably safer on the Mall than taking the Metro for the ride home.

I went to a friend's apartment in Arlington last year to see the fireworks. Great view from his balcony.

Oh really? Hmm, are you sure they were from the national mall? They might have been local ones?

those been there done that... too many people, metro gets packed.  

Had a great view of the airspace over the Mall. These were most definitely the DC fireworks, not anything local.

Sounds delightful 😊