U.S. 20 West - St. Anthony to Idaho Falls

U.S. 20 Business to St. Anthony branches west from U.S. 20 along Yellowstone Highway near Twin Groves.
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Measuring 2.92 miles in length, U.S. 20 Business runs west along Yellowstone Highway and Bridge Street south through Downtown St. Anthony.
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Old U.S. 20 continues 1.76 miles south from the diamond interchange at Exit 347 along Bridge Street and Yellowstone Highway to U.S. 20 at Exit 343.
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A series of three at-grade intersections remain along U.S. 20 between St. Anthony and Sugar City. U.S. 20 is a freeway otherwise southwest to Interstate 15 in Idaho Falls.
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U.S. 20 enters Madison County just ahead of the intersection with 2000 East / N 7th E. N 7th E south to Center Street is the pre-freeway alignment of U.S. 20 into Sugar City.
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Idaho Highway 33 combines with U.S. 20 west from the city of Teton at a diamond interchange (Exit 339) in Sugar City.
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Idaho Highway 33 travels 55.41 miles east from Sugar City to Driggs and the Wyoming state line south of Victor. Wyoming Highway 22 extends east from ID 33 to U.S. 191 in Jackson.
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A half diamond interchange (Exit 338) connects Center Street in Sugar City with U.S. 20 westbound ahead of this confirming marker.
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N Salem Road becomes N 2nd E south from the diamond interchange at Exit 337 into north Rexburg.
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ID 33 resumes west from U.S. 20 and Rexburg at Exit 333. ID 33 west to ID 28 north leads to U.S. 93 in the Lemhi County seat of Salmon. Construction in 2024 converted the exchange at Exit 333 into a DDI.
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ID 33 Spur follows Main Street east from Exit 333 to Downtown Rexburg. The 4.35 mile long route extends north along N 2nd E and Yellowstone Highway to Teton Island Canal and the Sugar City limits.
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The at-grade intersection connecting U.S. 20 with Bear World Road north was eliminated after 2016.
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U.S. 20 Business through the Jefferson County seat of Rigby runs 1.65 miles south from Exit 322.
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There is no direct access to Idaho Highway 48 from U.S. 20. Instead motorists are directed onto U.S. 20 Business south through Downtown Rigby to connect with the highway along 1st South. ID 48 comprises a 24.40 mile long route between I-15 at Roberts and U.S. 26 Business at Ririe.
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U.S. 20 Business from Rigby returns to U.S. 20 at a wye interchange (Exit 320) south of Burgess Canal.
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U.S. 20 enters the city of Ucon at the diamond interchange (Exit 315) with ID 43 south and 105th N.
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The diamond interchange at Exit 308 joins U.S. 20 west with Riverside Drive south along the Snake River and Fremont Avenue north ahead of the Idaho National Laboratory.
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U.S. 20 spans the Snake River west ahead of the folded diamond interchange (Exit 307) with Lindsay Boulevard.
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References:
Idaho Transportation Department (ITD). (2026, March 16). US-20 South St. Anthony Interchange. Retrieved from https://itdprojects.idaho.gov/pages/south-saint-anthony-interchange
Photo Credits:
- Alex Nitzman: 07/07/16
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Page Updated Wednesday March 25, 2026.
