1. Start at the trailhead, heading SW.
2. 50 ftPass Whitehall Reservoir.
3. 100 ftBear left onto Whitehall Yellow Trail, heading S.
4. 0.3 miTurn right, heading S.
5. 1.6 miTurn left onto Bridge Road, heading W.
6. 0.2 miBear right onto Whitehall Trail, heading S.
7. 50 ftContinue straight onto Bridge Road, heading S.
8. 0.1 miSharp right, heading SW.
9. 250 ftBear left onto Whitehall Trail, heading SW.
10. 0.3 miTurn right onto White Hall Road, heading S.
11. 0.2 miTurn left, heading N.
12. 250 ftBear right onto Grouse Trail, heading N.
13. 0.4 miSharp right onto Mammoth Rock Trail, heading NW.
14. 0.2 miPass Mammoth Rock.
15. 1.1 miBear right onto Spring Street Trail, heading N.
16. 0.7 miReach Mammoth Rock, then turn around and head back the way you came.
17. 0.7 miBear left onto Old Hopkinton Spring Trail, heading SE.
18. 1.3 miSharp left onto Grouse Trail, heading S.
19. 0.4 miBear left, heading E.
20. 250 ftTurn right onto White Hall Road, heading E.
21. 0.2 miTurn left onto Whitehall Trail, heading NE.
22. 0.3 miBear right, heading S.
23. 250 ftSharp left onto Bridge Road, heading S.
24. 0.1 miContinue straight onto Whitehall Trail, heading N.
25. 50 ftBear left onto Bridge Road, heading N.
26. 0.2 miTurn right onto Whitehall Yellow Trail, heading E.
27. 0.7 miBear right, heading NE.
28. 0.8 miBear right, heading NW.
29. 0.3 miBear right, heading E.
30. 50 ftArrive back at the trailhead.

Each distance is the walk from the previous step. Tap a step for a map of its junction.

Trail map, photos and weather for this hike: www.ambleway.com/hikes/mammoth-rock-whitehall-reservoir-out-back-20-km-b3cf