Physical Address
Jefferson Underground Building
2400 South Jefferson Avenue
St. Louis, MO 63104
(314) 596-2531
Mailing Address
Arch Reactor
PO Box 771643
Saint Louis, MO  63177-1643

We're equally easy to get to off of I-44 or I-55. You'll find us on the second floor of the Jefferson Underground Building, just north of the intersection of Gravois and South Jefferson.

The map below draws routes from the exits of I-44 and I-55 (marked with small, blue points) to the turn-in of the Jefferson Undergound's parking lot on the north side of the building.

For security reasons, the door to the building is kept locked at all times. Usually, we'll have a sandwich board sign set out with a doorbell. If not, check the mailing list/forums for details on who's phone to call for access.