BWI airport or DCA airport is the most convenient airports.  IAD is complicated.

From BWI: It is about 40min drive to the university. There is an express bus line that will take you to Greenbelt Metro for 31min. It runs every 40min. Time Table
From Greenbelt you can easily find taxis hanging aroud there, it will cost about $8 to get to the dept, 15min approx. Or you may take metro to College Park (just one station) and follow the direction below.
There are shuttle vans, but counting the waiting time it doesn't make much sense while the bus is running.

From DCA: Take Yellow line to Mt Vernon sq. (Do not take blue line) . Then transfer to Greenline (which will come to the same platform, the same side) to Greenbelt. Get off at College Park. Follow the direction below. About 1 hour altogether.

Bus, Metro: College Park metro station on green line.
Go out to the left, and wait for the bus at "UM Shuttle". This bus is free. Time Table.   You will see the bus will get into the gate of the university, then you get off at the first stop (stop#7). The building in front of you is math bldg.

From 95 North: It will split into 495 west and 495 east. Take 495 west, and then immediately exit to "College Park, Car pool". Follow the sign to College Park or Route 1. Take Route1 south for 2 miles. You will see campus on your right. The gate will be at the corner of Paint branch Pkwy and Route 1. Take right to get into campus.
From 495 East, West: Exit at College Park and follow the direction above.
From 295 North: Exit at Greenbelt. Take 193 West, and go about 3 miles. Either follow the sign to Route1 south and follow the direction above, or ignore Route 1, keep going for 0.5 miles more and find a a gate to campus: Paint Branch Dr on your left.
Other directions:

There are metered parking (50c/hour) and casher attended parking lot ($1/hour, maximum $8/day. ) It is in front of AV Williams building, called Paint Branch Drive Visitor Lot. Check the map:
Street parkings are available around north east of campus. No Meter. Free.

10min walk:From Route 1, turn east at Bestwestern hotel, and turn immediately right (south) onto 48th ave. There are many street parkings around there.
5min walk: There are some spots behind the fire company just at the enterance of the university.
5min walk: next to fire company there is a small mall with parking. Park at your own risk. Could be towed.
7min walk: There is McDonald with parking, too, along Route 1. Again, park at your own risk.

After 4pm, most of on-campus parking lots become available  for free to anyone. The closest to the math building is lot XX: turn right after the gate, and then you find it immediately on your right. Regents Dr. Parking garage is also close: check the map.
There are many others. Check the sign: it says "you are welcome to park after xyz with or without permit."


There will be a discount for staying at quality inn (10 min walk from the dept: 7200 Baltimore Avenue, College Park, MD 20740. Phone: 301-864-5820). Reservation has to be through May is a busy season, reserve soon !!!