|Length||715 mi[ citation needed] (1,151 km)|
|Existed||1926[ citation needed]–present|
|West end||US 64 / US 70 / US 79 at Memphis, TN|
|East end||Line Street at Charleston, SC|
|States||Tennessee, Mississippi, Alabama, Georgia, South Carolina|
U.S. Highway 78 is an east–west United States highway that runs for 715 miles (1,151 km) from Memphis, Tennessee, to Charleston, South Carolina. From Byhalia, Mississippi to Birmingham, Alabama, US 78 is designated as Interstate 22. The highway's western terminus is at U.S. Route 70 (Second Street) in Memphis, Tennessee, and its eastern terminus is on Line Street, in Charleston, South Carolina.
US 78 runs along Linden Avenue, Somerville Street, E. H. Crump Boulevard, and Lamar Avenue through Memphis, Tennessee. In Tennessee, US 78 is historically known as Pigeon Roost Road, and some aborted sections of the highway in Mississippi also claim that name as well as Lamar Avenue. Throughout the Tennessee portion, US 78 is overlapped in its entirety by State Route 278 (SR 278), along Linden Avenue and Somerville Street, and State Route 4 (SR 4) along E. H. Crump Boulevard and Lamar Avenue. 
US 78 is a freeway for its entire length in Mississippi. The section from its intersection with Interstate 269 in Byhalia, Mississippi to the Alabama state line is designated as Interstate 22. The highway runs across the northeastern rural part of the state, connecting several population centers. Mississippi's portion of US 78 is defined in Mississippi Code Annotated § 65-3-3. The old routing of US 78 through the state is signed as MS 178.
US 78 is a major east–west state highway across the central part of Alabama. It is internally designated "State Route 4" (SR 4) by the Alabama Department of Transportation, though the only section of State Route 4 that is signed is along portions mainly west of Jasper. The section from the Mississippi state line to Interstate 65 near Birmingham, Alabama is designated as Interstate 22. East of Birmingham to the Georgia state line, US 78 has been replaced as a major through-route by Interstate 20. The two routes roughly parallel each other, with junctions at Leeds and Pell City. 
speculation?] West of Jasper, old US 78 is signed as AL 118 to Guin, and the segment from Guin northward to I-22 at Hamilton is signed as US 43/US 278.[
US 78 enters Georgia in Haralson County, and then proceeds through Carroll County and Douglas County. In Douglasville, located in Douglas County, US 78 runs through the downtown, historical part of the city. It is the original thoroughfare for these Georgia counties.
There is another short freeway portion east of Atlanta, leading from just inside (west of) I-285 (the Perimeter) eastward to the suburbs of Stone Mountain, Georgia, and Snellville, Georgia. This portion is named the Stone Mountain Freeway, and has an excellent view of Stone Mountain while traveling eastbound. Along this route, US 78 is largely conterminous with Ponce de Leon Avenue.
The route then continues eastward through DeKalb, Gwinnett, Walton, and Oconee counties. In Oconee county US 78 leaves Moina Michael Highway at the SR 316 interchange, turning right and running concurrent with SR 316/ US 29. (From this point, Moina Michael Highway is signed as US 78 Business, which follows the original route of US 78 through Athens, Ga.) At the terminal eastern interchange of SR 316 both US 78 and US 29 turn right and join with SR 10 Loop, a mostly interstate-grade bypass that rings Athens-Clarke County. US 78 exits the bypass and turns right at the Lexington Road interchange. From there US 78 passes through Oglethorpe, Wilkes, McDuffie and Columbia Counties into Augusta and then onto one of the twin bridges across the Savannah River into South Carolina. 
US 78 provides the most direct route between Augusta and Charleston, through the South Carolina Lowcountry. Crossing Savannah River into the state, it goes northeast into Aiken before going southeasterly through the cities and towns of Williston, Blackville, Denmark, Bamberg, Branchville, and St. George. East of Dorchester, it parallels Interstate 26 into downtown Charleston, where it ends. 
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In western Alabama, the historical name of US 78 is Bankhead Highway. It is also known by this name in portions of Georgia, including Atlanta, and the Bankhead neighborhood takes its name from that stretch of road. Also, the old section of US 78 (now MS 178) that travels through downtown New Albany, Mississippi, is named Bankhead Street.
Throughout the 2000s, US 78 has been gradually upgraded into a four-lane freeway in Mississippi and Alabama and signed as Interstate 22. US 78 is completely concurrent with I-22 from Byhalia, Mississippi to Birmingham, Alabama.
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After the completion of Interstate 22 throughout the 2010s, it is uncertain whether US 78 will be decommissioned west of Birmingham or the old route recommissioned as US 78 upon completion of Interstate 22. If the old route is recommissioned as US 78, parts of I-22 and US 78 would be forced to overlap. A stretch from just west of Hamilton, Alabama to the first exit in Mississippi, as well as a stretch from MS 25 in Fulton, Mississippi to the next exit west of Fulton after crossing the Tennessee-Tombigbee waterway will overlap. The Hamilton area overlap would be due to the old US 78 routing no longer exists west of Hamilton having been upgraded to I-22 from Weston westward into Mississippi. The second overlap would be necessary because the old US 78 no longer exists west of downtown Fulton, Mississippi due to the Tennessee-Tombigbee waterway and no bridge in place to carry US 78 traffic on the former route.
- US 64 / US 70 / US 79 in Memphis
- I‑240 in Memphis
- US 51 in Memphis
- I‑240 in Memphis
- I‑22 / I‑269 west-northwest of Byhalia. Begin I-22 Concurrency.
- US 45 in Tupelo
- US 43 / US 278 in Hamilton
- Future I‑222 / Future I‑422 near Adamsville
- I‑22 / I‑65 near Birmingham. End I-22 Concurrency.
- I‑20 / I‑59 in Birmingham
- US 11 in Birmingham. The highways travel concurrently through Birmingham.
- US 31 / US 280 in Birmingham
- I‑20 in Leeds
- US 411 in Leeds
- I‑20 northwest of Cooks Springs. The highways travel concurrently to Pell City.
- US 231 in Pell City
- I‑20 in Riverside
- US 431 in Oxford.
- US 27 in Bremen
- US 278 in Lithia Springs. The highways travel concurrently to Druid Hills.
- I‑285 in Atlanta
- US 19 / US 41 in Atlanta. The highways travel concurrently through Atlanta.
- US 19 / US 29 / US 41 in Atlanta. US 29/US 78 travels concurrently to the Scottdale– North Decatur city line.
- US 23 in Atlanta. The highways travel concurrently to Decatur.
- I‑285 on the Scottdale– Clarkston city line
- US 29 southeast of Bogart. The highways travel concurrently to Athens.
- US 129 / US 441 in Athens. The highways travel concurrently through Athens.
- US 378 in Washington
- I‑20 north of Thomson
- US 278 southeast of Thomson. The highways travel concurrently to Clearwater, South Carolina.
- US 221 in Harlem
- I‑520 in Augusta
- US 1 in Augusta. The highways travel concurrently to Aiken, South Carolina.
- US 25 in Augusta. The highways travel concurrently to North Augusta, South Carolina.
- South Carolina
- I‑520 in North Augusta
- US 321 in Denmark
- US 301 / US 601 in Bamberg
- US 21 in Branchville. The highways travel concurrently through Branchville.
- I‑95 in St. George
- US 15 in St. George
- US 178 east of Dorchester
- I‑26 in North Charleston
- US 52 in North Charleston. The highways travel concurrently through North Charleston.
- I‑26 in North Charleston
- I‑526 in North Charleston
- King Street/Line Street in Charleston
- Google (April 11, 2014). "Route of US-78 in Tennessee" (Map). Google Maps. Google. Retrieved April 11, 2014.
- Google (April 11, 2014). "Route of US 78 in Alabama" (Map). Google Maps. Google. Retrieved April 11, 2014.
- Google (April 11, 2014). "Route of US 78 in Georgia" (Map). Google Maps. Google. Retrieved April 11, 2014.
- Google (April 11, 2014). "Route of US 78 in South Carolina" (Map). Google Maps. Google. Retrieved April 11, 2014.
|Wikimedia Commons has media related to U.S. Route 78.|
- Evermore Community Improvement District
- High Priority Corridors @ aaroads.com
- Highway 78 CID
- Highway 78 on OpenStreetMap.org
- Endpoints of U.S. Highway 78
|Browse numbered routes|
|← SR 77||TN||SR 78 →|
|← MS 76||MS||US 80 →|
|← SR 77||AL||SR 79 →|