Combine first 6 ingredients; set aside.
Combine water and vinegar in equal amounts to a depth of 1 inch in a very large pot with a lid; bring to a boil.
Place a rack in pot over boiling liquid; arrange half of crabs on rack.
Sprinkle with half of seasoning mixture.
Top with rest of crabs, and sprinkle with remaining seasoning mixture.
Cover tightly, and steam 20 to 25 minutes or until crabs turn bright red.
Rinse and drain well, if desired.
Serve hot or cold.