The last place I saw a rattlesnake was at a CoE day use area in Thomaston, CT. Also saw several copperheads in CT. Those I don't like.
But water moccasin's in the swampy south are the worst.
Rattlesnakes are the most predictable, easiest to spot and avoid of the US snakes in my opinion.
They love sun when it is cool, shade when it is hot. As mentioned many times, don't put your hands or feet anywhere you cannot see.
Snakes try to avoid large animals, like people. But they can't really hear. they feel vibrations in the ground. Walk heavy in snake country. Keep a wary out when hiking and walk away if you see one.
Frankly, I'm more afraid of NM and AZ drivers than I am of snakes.
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One other point - killing a snake in a national park without residual evidence that you or one of your party was threatened can be a felony. People are required to attempt to the highest degree possible to avoid animals, especially dangerous animals. Injuring or killing an animal is only permissible after all other possible, not 'reasonable', attempts to break off or avoid contact have failed.