Originally Posted by
paytonc
MARC does not run on weekends or most holidays (yet; this will change). Amtrak does run on 4 July, but will be expensive as it's a holiday.
WMATA's buses, including the B30 ($6), operate on a Saturday schedule on the 4th, which on that route means business as usual since M-Sa schedules are similar. The bus runs pretty much on schedule, in my experience. Then you'll transfer to the Green Line, which is $4.50 to downtown DC.
Perhaps my time's less valuable, but I'd fly out of BWI to save $50, or if it meant the difference between a saver/standard award.
I refuse to use those WMATA buses. The schedule is inadequate and I have had too many experiences with the bus being 1+ hour late, excessive overcrowding, etc. The overcrowding will be especially bad on a holiday weekend.
If you insist on going to BWI, use Supershuttle, but DCA is by far the superior option in virtually every way.