U.S. Highway 18
US 18 highlighted in red
Route information
Maintained by SDDOT
Length	451.88 mi[1] (727.23 km)
Existed	1926–present
Major junctions
West end	US 18 at the Wyoming state line near Edgemont
Major intersections	US 385 from Hot Springs to Oelrichs US 83 in Mission US 183 from Jordan Junction to Colome US 281 from near Fairfax to near Armour US 81 near Freeman I-29 near Worthing
East end	US 18 at the Iowa state line near Canton
Location
Country	United States
State	South Dakota
Counties	Fall River, Oglala Lakota, Bennett, Todd, Tripp, Gregory, Charles Mix, Douglas, Hutchinson, Turner, Lincoln
Highway system
United States Numbered Highway System List Special Divided South Dakota State Trunk Highway System Interstate US State
← SD 17 → SD 18

U.S. Highway 18 (US 18) is a part of the United States Numbered Highway System that travels from Orin, Wyoming, to Milwaukee, Wisconsin. In the state of South Dakota, US 18 runs from the Wyoming border east to the Iowa border.

Route description

US 18 enters South Dakota west of Edgemont. It passes through Hot Springs, the Pine Ridge Indian Reservation, the Rosebud Indian Reservation, Winner, and Gregory, before crossing the Missouri River near Pickstown over Fort Randall Dam. East of the Missouri River, US 18 passes through (or near) Lake Andes and Tripp before a brief concurrency with Interstate 29 (I-29) near Worthing. East of I-29, US 18 passes through Canton before crossing the Big Sioux River into Iowa.^[2]

The South Dakota section of US 18 is legally defined at South Dakota Codified Laws § 31-4-141.^[3]

History

Major intersections

County	Location	mi[1]	km	Destinations	Notes
Fall River	​	0.00	0.00	US 18 west – Lusk	Continuation into Wyoming
	Edgemont	12.10	19.47	SD 471 south – Edgemont, Provo	Northern terminus of SD 471
	​	24.18	38.91	SD 89 north – Custer	Southern terminus of SD 89
	Hot Springs	39.82	64.08	SD 71 south – Ardmore	Northern terminus of SD 71
		40.54	65.24	US 385 north – Mount Rushmore, Wind Cave National Park	Western end of US 385 concurrency
	Maverick Junction	44.67	71.89	SD 79 north – Rapid City	Western end of SD 79 concurrency
	Oelrichs	62.27	100.21	US 385 south / SD 79 south – Chadron	Eastern end of US 385/SD 79 concurrency
Oglala Lakota	Pine Ridge	103.53	166.62	SD 407 south – Rushville	Northern terminus of SD 407
	​	120.99	194.71	SD 391 south – Gordon	Northern terminus of SD 391
Bennett	Martin	148.94	239.70	SD 73 south – Merriman	Western end of SD 73 concurrency
	​	161.42	259.78	SD 73 north – Kadoka	Eastern end of SD 73 concurrency
Todd	​	189.98	305.74	SD 63 north – Parmelee, Norris	Southern end of SD 63
	​	206.35	332.09	US 83 north – White River	Western end of US 83 concurrency
	Mission	209.69	337.46	US 83 south – Valentine	Eastern end of US 83 concurrency
Tripp	​	242.54	390.33	SD 53 south – Clearfield	Western end of SD 53 concurrency
	Jordan Junction	243.54	391.94	US 183 north / SD 44 west / SD 53 north – Presho	Western end of US 183/SD 44 concurrency; eastern end of SD 53 concurrency
	Winner	252.70	406.68	SD 44 east – Platte	Eastern end of SD 44 concurrency
	Colome	263.34	423.80	US 183 south / SD 49 north – Bassett	Eastern end of US 183 concurrency; Southern terminus of SD 49
Gregory	Gregory	277.92	447.27	SD 47 north / SD 251 south to I-90	Western end of SD 47 concurrency; Northern terminus of SD 251
	Burke	286.03	460.32	SD 47 south – Jamison	Eastern end of SD 47 concurrency
	​	305.22	491.20	SD 1806 north – Whetstone Bay	Southern terminus of SD 1806
	​	311.99	502.10	SD 43 south – Butte	Northern terminus of SD 43
	​	320.78	516.25	US 281 south – Spencer, O'Neill	Western end of US 281 concurrency
Charles Mix	Pickstown	332.90	535.75	SD 46 east (297th Street) – Wagner	Western terminus of SD 46
	Lake Andes	338.98	545.54	SD 50 west – Geddes, Platte	Western end of SD 50 concurrency
	​	348.90	561.50	SD 50 east – Wagner	Eastern end of SD 50 concurrency
	​	355.87	572.72	US 281 north – Armour	Eastern end of US 281 concurrency
Douglas	No major junctions
Hutchinson	​	373.94	601.80	SD 37 – Tripp, Parkston
	​	387.70	623.94	SD 25 south – Scotland
	​	402.77	648.20	US 81 – Freeman, Yankton
Turner	​	419.82	675.63	SD 19 south – Viborg	Western end of SD 19 concurrency
	​	420.81	677.23	SD 19 north – Hurley	Eastern end of SD 19 concurrency
Lincoln	Lincoln–Lynn township line	435.23	700.43	I-29 south – Beresford	Western end of I-29 concurrency; I-29 exit 62
	Lynn Township	438.25	705.30	I-29 north – Sioux Falls	Eastern end of I-29 concurrency; I-29 exit 59
	​	441.72	710.88	SD 115 north / CR 121 south (474th Avenue) – Sioux Falls	Southern terminus of SD 115
	​	445.71	717.30	SD 11 north (478th Avenue) – Sioux Falls	Western end of SD 11 concurrency
	​	446.67	718.85	SD 11 south (479th Avenue) – Alcester	Eastern end of SD 11 concurrency
	Canton Township	451.88	727.23	US 18 east – Inwood	Continuation into Iowa
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus