AMP: 0 Location: S-320 and US-12, Fallon Cty No reassurance shield as the highway begins. 320 is a quick spur up to Ismay. AMP: 4 Location :S-320 at the Fallon County Line, Custer Cty As we enter Custer County, the road picks up the CR 351 designation AMP: 6 Location: Main St and 6th St, Ismay S-320 ends … Continue reading Montana Secondary Highway 320, US-12 to Ismay