The drain pipe which my washer emptied into was overflowing.
I was able to fix this problem by disassembling as much as the PVC piping and snaking the drain it attached to. I then put a "lint guard" on the pipe so it hopefully won't happen again.
One problem- I pulled this black crap out of the drain, whatever it was seems to have made me sick. Has this happened to anyone before? Is it mold? The "sickness" is basically cold symptoms but it is an odd problem.