Answer: It sounds to me that you saw a Dolomedes spider. These spiders are reasonably common, don't spin a web to catch food but instead run after their prey. These spiders, like all spiders, do have some venom but are not dangerous. Only two species of spiders in North America are considered dangerous (Black Widow and Brown Recluse) and these both make webs and do not crawl about on the ground.
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