Georgia State Route 142 runs in a southerly direction with a northern starting point at Georgia State Route 81 in Newton County, Georgia, just north of Covington, then running through eastern Jasper County, and ending in Putnam County at Georgia State Route 16 just west of Eatonton. It is locally known as the John R. Williams Highway in Newton County, and the Shadydale Highway in Putnam County. A $12 million widening project was announced in 2009 with a scheduled completion in 2012.

The route is co-signed for 2.3 miles (3.7 km) with US 278 and SR 12 just east of Covington.