Editing U.S. Route 12 (section)

===South Dakota===
{{Main|U.S. Route 12 in South Dakota}}
US&nbsp;12 enters South Dakota from North Dakota as a rural two-lane highway about {{convert|10|mi|km}} west-northwest of [[Lemmon, South Dakota|Lemmon]] before entering the [[Standing Rock Indian Reservation]]. For approximately the next {{convert|70|mi|km}}, US&nbsp;12 runs parallel to the border of North Dakota, sometimes within less than {{One2a|{{convert|1|mi|km|spell=in}}}}. At [[Walker, South Dakota|Walker]], US&nbsp;12 heads southeast for {{convert|37|mi|km}}, where it crosses the [[Missouri River]] at [[Mobridge, South Dakota|Mobridge]], exiting the reservation. From there, it continues east for {{convert|18|mi|km}}, until it meets with [[U.S. Route 83|US&nbsp;83]] near [[Selby, South Dakota|Selby]]. It overlaps US&nbsp;83 for {{convert|7|mi|km|spell=in}}. After leaving US&nbsp;83, it turns due east and spends about {{convert|80|mi|km}} as a rural two-lane highway again. A few miles before reaching [[Aberdeen, South Dakota|Aberdeen]], it becomes an at-grade expressway. After the junction with [[U.S. Route 281|US&nbsp;281]], it goes back to being two lanes for a few miles through Aberdeen and past [[Aberdeen Regional Airport]], before once again becoming a four-lane expressway, until {{convert|2|mi|km|spell=in}} before [[Waubay, South Dakota|Waubay]]. East of Waubay, it becomes again an at-grade expressway until it meets with [[Interstate 29|I-29]] near [[Summit, South Dakota|Summit]]. The speed limit from Aberdeen to I-29 is {{convert|70|mph|km/h|abbr=on}} except through the communities of [[Groton, South Dakota|Groton]], [[Webster, South Dakota|Webster]], and Waubay. From there, it heads southeast {{convert|22|mi|km}} until [[Milbank, South Dakota|Milbank]]. At Milbank, it continues east for {{Convert|12|mi|km}}, until it crosses into [[Minnesota]] at [[Big Stone City, South Dakota|Big Stone City]], just south of [[Big Stone Lake]]. The South Dakota section of US&nbsp;12 is legally defined at South Dakota Codified Laws § 31 April 132.<ref>{{cite web |url= http://legis.state.sd.us/statutes/DisplayStatute.aspx?Type=Statute&Statute=31-4-132 |title= 31-4-132. U.S. Highway 12 from North Dakota to Minnesota |work= South Dakota Statutes |access-date= January 7, 2007 |archive-date= February 13, 2007 |archive-url= https://web.archive.org/web/20070213122942/http://legis.state.sd.us/statutes/DisplayStatute.aspx?Type=Statute&Statute=31-4-132 |url-status= live }}</ref>