Worth stopping in Yellowstone Park at end of October?

Here's the park's web site. Most roads will be closed around early November. If it's not too far out of your way and the weather reports look favorable, definitely go. West Yellowstone is open all year because that's where the snowmobile trips originate.

Mammoth campground in the park is open year-round. Come prepared with full water tank and empty grey/black as the water might be turned off throughout the park.

https://www.nps.gov/yell/planyourvisit/parkroads.htm