Mark from Saint Louis, MO 63144 on 2/2/2025 9:20:56 PM:
Unfortunately, in this day and age, I'd never go out on a limb to say any parking place is "secure" anywhere. But when I rode the trail from Deadwood to Edgemont and back in 2023, I parked at the trailhead in Deadwood. It is literally next to the Mickelson Trailhead sign at mile marker 109 in Deadwood. Off US 85. If I recall correctly, there are about 250 free parking spots there in an open parking lot. Other than my Kuat bike rack and some clothes, I didn't leave anything of value in my SUV. Everything was fine when I returned. I'm assuming there are cameras there, but I don't know that for a fact.
I believe you can park at some of the casino farther down Hwy 85, but I believe they all charge a daily fee. Same with some of the local hotels.
When I go back to ride again this summer, I plan to use the same parking lot I used before - right next to the trailhead. And hope I have the same luck. Good luck to you.