AMP: 0 Location: US-18 and US-85, Niobrara Cty Reassurance shield as US-18 splits from US-85. This is the first time in its existence that US-18 will run completely alone AMP: 10 Location: US-18 at the South Dakota State Line, Niobrara Cty A few miles later, US-18 will enter South Dakota and continue its journey eastward … Continue reading U.S. Route 18, US-85 to SD State Line