What kind of spider was this?

Impossible question to answer from your description, we would need to see a photo. To answer your second question, yes, it's poisonous--all spiders have venom, that's how they immobilize and eat their prey. However, is it dangerous to humans? That's another question. In the U.S. there's really only two that are considered dangerous to humans--the Brown Recluse and the Black Widow. For most spiders here in the U.S., their fangs aren't long enough to penetrate the outer layers of your skin, and even if they do, the amounts of poison they could inject are not enough to cause anything more than a week or two's worth of soreness/itching.