South Dakota State Route 48 is a east-west highway in Central Union County. This runs from Interstate 29 to the South Dakota/Iowa State Line. SD St Rt 48 passes through the following town in Union County. Spink SD St Rt 48 is not multi-plexed in Union County. SD St Rt 48 intersects the following highways in Union County. Interstate 29, near Spink. South Dakota State Route 11, near Spink.