Saltville, the Confederacy's leading producer of salt, became a major Federal target during the Civil War. Confederate Gen. Sam Jones proposed defenses there in June 1863, and construction began that year. The defenses included a half dozen earthen forts, hundreds of yards of trenches, several arsenals, and camps for troops. Picket posts guarded the roads leading out of Saltville, and additional posts guarded the bridges and culverts of the Virginia and Tennessee Railroad and the Saltville branch line. Well-preserved remains of hilltop forts and hundreds of yards of trenches still survive on the hills around Saltville Valley. Saltville Valley had once been part of an ancient riverbed, and bones and teeth of Ice Age animals extinct 10,000 years ago have been collected there since the late 1700s. Salt water gave the town its name and drew giant mammals, Native Americans, colonial settlers, Confederate and Union armies, and later industrial development into the 20th century. Commercial salt production began in the 1780s with open wells that supplied brine, furnaces where it was boiled in iron kettles, and salt buildings for storage. Before the Civil War, the salt works used only a few furnaces, but during the war three dozen furnaces fired 2,600 kettles, and production rose from 150,000 bushels per year before the war to four million bushels in 1864. The site also lay a few feet from the Smyth/Washington County Line drawn in 1832 between the original Preston/King Saltworks so both counties could share the revenues, and it was the site of the first attempt to mine salt in the United States, an effort that failed as operators continued to rely on wells.