Winslow Visitor's Center

Free overnight parking on a level lot that's mostly gravel, but paved near the visitor's center.

Tons of room, easy enough to pull into you could do it at night (I recommend pulling into the paved entrance by the visitor's center building if you do come in at night). It seems fine to overnight even if you come in after the center closes.
I was happily surprised to find the nice wide walkway to town (walk toward the train tracks around the sports/amphitheater field) with trees and historical displays, it's rare to get a nice place to walk at a free overnight spot. Pets and bikes are allowed, and 'the corner' isn't very far.
The nearby train tracks weren't loud, but the trains did make random clunking/low vibrational sounds. This didn't bother me, but might bother sensitive sleepers.

The people in the Tourist Center couldn't have been any nicer. The woman behind the counter got me a map and gave directions to "the corner" and suggested I take the walking path behind the center. I did and it was a pleasant walk through a park. Just 4 blocks to "the corner." When we arrived, there were many tourists getting their photos taken and everyone was friendly and several people offered to take a photo of me and my dog.
There wasn't much else in town. A couple restaurants/bars/coffee shops. Everyone was friendly.

The parking lot itself is paved and level. My old propane fridge must be totally level to work and I had no trouble finding a totally level spot in the back corner that worked without the need for leveling blocks. Adjacent to the center lot is a HUGE gravel lot, perfect for larger rigs, or if it was crowded, you could spread out. It is next to a very active train track, but no loud whistles or horns...just a (to me) soothing rumble all night long.

The parking lot emptied out about 4:30 when the tourist center closed, and then re-filled about 6:30 at night. They aparently had some sort of council meeting? One other truck camper pulled in, about 4 spaces from me, climbed in the back of the camper and was quiet all night. We did have a giant (think Greyhound Bus) class A pull in between us at midnight, blazing their high beams through our bedroom windows, and running the dieslel engine until they got their slides out and made sure they woke us up. They could have easily pulled in at the opposite end of the gravel lot and not disturbed anyone, but their rudeness certainly doesn't reflect on the Tourist Center. Assholes can show up anywhere, right?

Good Verizon coverage.

Convenient and easy stop to park off the interstate for the night. We arrived after the visitor center closed and parked along the edge of the paved area. There were a bunch of trailers carrying carnival rides in the gravel part of the parking lot, not sure if they were passing through or getting ready to set up/break down but they kept quiet all night.

There is a train track directly behind the parking lot but it didn’t bother us- more just rumbling trains going by, no whistle blowing.

Stayed here May and then again June 2021. Perfect overnight stop. Large, paved parking lot, plus a large adjoining gravel lot. We parked in the back (SW) corner of the paved lot. Easy 4-block walk into the center of town. Yes, trains throughout the night but they didn’t really bother us. Also suggest taking the time to go into the Visitor Center which has an interesting history as a trading post and warehouse for the Hubbell Trading posts in the area. The woman at the desk was very nice and gave us a bit of a personal tour of the building. One night we were alone in the parking lot, on our second stay there was one another RV.