The "secret" designation for US 19 in Florida, between Memphis and Perry, is SR 55. Between Perry and Capps, it follows SR 20, and between Capps and the Georgia border, it follows State Road 57.
According to a Dateline NBC study, part of US 19 in Florida is the most dangerous road in the United States. A Highway Patrol test period beginning in 1998 and ending in 2003, as mandated by the National Highway Traffic Safety Administration, showed the stretch of US 19 from Pasco County to Pinellas County to average approximately 52 deaths a year, or 262 deaths in the 5-year duration of the study. 100 of these deaths were pedestrian related making US 19 the #1 worst road to walk on in these two counties. Multiple efforts to improve US 19 have been suggested to the FDOT, among them, an overpass strictly for left-turn lanes.
Currently, US 19 between Clearwater and Pinellas Park is getting a freeway-style upgrade due to the cancellation of an extension of Interstate 375 in the late 1970s.
US 19 pursues an independent path in Georgia, with Interstate 75 as much as 50 miles (80 km) away.
From the north side of the state, the first town it passes through is Blairsville. After about 37 miles (60 km) of extremely curvy road, it arrives in Dahlonega, where it becomes concurrent with SR 400. Prior to the realignment to become concurrent with SR 400, US 19 was what is now known as SR 9; traveling through the town centers of Dawsonville, Cumming, Alpharetta, and Roswell. Most of this section (US 19/SR 400) is a limited access highway with 2 lanes in each direction, becoming 4-lanes in each direction as the highway travels through the northern suburbs of Atlanta.
At the junction with I-285's north side, it once again switches to become concurrent with SR 9 (Roswell Road), about 1.5 miles (2.4 km) west. It follows Roswell Road south through the city of Sandy Springs and enters Atlanta from the north side of the city. After several miles, it intersects with SR 141 in Buckhead. This is also where Roswell Road ends and becomes Peachtree Street. After continuing south on Peachtree Street, it becomes Spring Street in Midtown. It turns west onto 14th Street for a few miles and then turns south again and becomes concurrent with US 41 through Downtown Atlanta and Metropolitan Parkway (formerly Stewart Avenue) through the south side of the city.
US 19 starts again in Bluff City, heading northeast along the Volunteer Parkway (and concurrency with US 11E) to Bristol. In downtown Bristol, US 19 crosses the Tennessee/Virginia state line on State Street.
US 19 overlaps with three corridors that are part of the Appalachian Development Highway System (ADHS), which is part of Appalachian Regional Commission (ARC). Passed in 1965, the purpose of ADHS is to generate economic development in previously isolated areas, supplement the interstate system, connect Appalachia to the interstate system, and provide access to areas within the Region as well as to markets in the rest of the nation.
In North Carolina, US 19 was NC 10 from the Georgia line to Asheville, N.C. Highway 29 from Asheville to Madison County, N.C. Highway 69 to a point near the Tennessee line, and either N.C. 194 or N.C. 694 for a short distance south of the Tennessee line.
The original U.S. 19 in Yancey, Mitchell and Avery Counties mostly followed the route now designated 19E. U.S. 19W in Yancey County was U.S. 19-23 in 1935, and what is now U.S. 19E was US 19A. The 19E and 19W designations have been used since 1930.
US 19 first entered Florida in 1929. It underwent two route shifts, the first in 1933 and the second in 1946, which adjusted it to its current alignment. US 19 was extended to its southern terminus of Memphis in September 1954, when the original Sunshine Skyway Bridge opened to traffic.
Prior to 1948, U.S. 19 between Ela and Waynesville essentially followed the route of present-day US 74. Then this road was called U.S. 19 Alternate (U.S. 19-A) and the section of NC 28 From Ela to Cherokee and the section of N.C. 293 from Cherokee to near Waynesville became U.S. 19. Improvements were made, including a new section of highway west of Lake Junaluska.
Around 1956, U.S. 19-23 was widened to four lanes from Lake Junaluska to Canton.
In January 1983, after improvements to U.S. 19-A had made it similar to an Interstate Highway, the state proposed designating U.S. 19-A as U.S. 19 Bypass. At one point changing U.S. 19-A to U.S. 19 was considered, but businesses in Maggie Valley opposed the idea of their highway being changed to U.S. 19-A. U.S. 19-A became the Great Smoky Mountains Expressway.
The planned St. Petersburg-Clearwater Expressway, or Pinellas Beltway, would have followed the current alignment of "Alt 19" from I-275 to Clearwater, Florida. The intersection of Seminole Boulevard and Bay Pines Boulevard is a remnant of this proposed road. The beltway road was proposed in 1974, but it was dead by 1980.