The rivers were a major means of commercial transportation during the 1700s and early 1800s for traders coming up from the coast. When they reached the Fall Line, their boats could go no farther because of the falls. So, they unloaded their goods at those points and set up trading posts.
Several of those sites became cities — Columbus, Macon, Milledgeville, Augusta. Some of them also became industrial centers because the falling water provided abundant hydropower for factories.
In essence, the Fall Line represents the prehistoric seashore of some 50 million years ago, when the ocean covered most of Georgia's southern half. Marine fossils tens of millions of years old still can be found along the Fall Line.
The line also marks major differences in soil types, wildlife habitats, vegetation, hydrology and other natural characteristics. Clay soils dominate to the north; sandy soils to the south.
The Fall Line has one other distinction: It's also known as the "gnat line." Gnats reproduce best in the Coastal Plain's moist, sandy soils but not so well in the Piedmont's clay soils.
In the sky: The moon will be last quarter Aug. 9, said David Dundee, astronomer at Tellus Science Museum. Mercury is low in the east just before sunrise. Venus rises out of the east about three hours before sunrise. Mars is low in the west just after dark and sets in the west a few hours later. Jupiter rises out of the east about four hours before sunrise. Saturn is low in the west at dark and sets a few hours later.
IF YOU GO
High Falls State Park. 1,050-acre park named for tumbling cascades and waterfall on the Towaliga River in Monroe County. In the early 1800s, High Falls was a prosperous industrial town with several stores, a grist mill, cotton gin, blacksmith shop, shoe factory and hotel. It became a ghost town in 1880s when a major railroad bypassed it. Visitors can hike along the river's edge and through hilly forest to the remains of a power plant. Boat rental, ramps and fishing docks provide access to a 650-acre lake. Overnight visitors can choose from a spacious campground or lakeside yurts, which are like canvas and wood tents. 76 High Falls Park Drive, Jackson. 478-993-3053, www.gastateparks.org/HighFalls. Directions: Exit 198 off I-75; go 1.8 miles east on High Falls Road. $5 parking fee. Hours: 7 a.m. to 10 p.m. daily. Office hours: 8 a.m. to 5 p.m. daily.