AMP: 45 Location: US-287 and S-408, Teton Cty Reassurance shield after the S-408 junction. AMP: 40 Location: US-287 and MT-21, Lewis & Clark Cty After we enter Lewis & Clark County, we’ll approach Montana 21. AMP: 40 Location: US-287 and MT-21, Lewis & Clark Cty Follow 21 east to Great Falls. Stay on 287 for Helena. MT-21 is … Continue reading U.S. Route 287, S-408 to MT-21