AMP: 0 Location: Big Powder River Rd and US-212, Powder River Cty No reassurance shield as S-398 begins. AMP: 5 Location: Big Powder River Rd and Turnbough Rd, Powder River Cty Not sure what this sign is supposed to symbolize, but we are two miles from the turnoff up the Powderville Road. AMP: 7 Location: Big Powder River … Continue reading Montana Secondary Highway 398, US-212/MT-59 to Powderville Rd