Placer gold mining was soon joined by hard rock mining, as prospectors followed the gold to its source veins in the hills. Gold in some upper gravel benches east of the Blue River was recovered by hydraulic mining. Gold production decreased in the late 1800s, but revived in 1908 by gold dredging operations along the Blue River and Swan River. The Breckenridge mining district is credited with production of about one million troy ounces (about 31,000 kilograms) of gold. The gold mines around Breckenridge are all shut down, although some are open to tourist visits. The characteristic gravel ridges left by the gold dredges can still be seen along the Blue River and Snake River, and the remains of a dredge are still afloat in a pond off the Swan River. Notable among the early prospectors was Edwin Carter, a log cabin naturalist who decided to switch from mining to collecting wildlife specimens. His log cabin, built in 1875, still stands today and has been recently renovated by the Breckenridge Heritage Alliance with interactive exhibits and a small viewing room with a short creative film on his life and the early days around Breckenridge. Harry Farncomb found the source of the French Gulch placer gold on Farncomb Hill in 1878. His strike, Wire Patch, consisted of alluvial gold in wire, leaf and crystalline forms. By 1880, he owned the hill. Farncomb later discovered a gold vein, which became the Wire Patch Mine. Other vein discoveries included Ontario, Key West, Boss, Fountain, and Gold Flake. The Breckenridge Heritage Alliance reports that in the 1930s, a women's group in Breckenridge stumbled upon an 1880s map that failed to include Breckenridge. They speculated that Breckenridge had never been officially annexed into the United States, and was thus still considered "No Man's Land". This was completely false—official US maps did include Breckenridge—but these women created an incredibly clever marketing campaign out of this one map. In 1936 they invited the Governor of Colorado to Breckenridge to raise a flag at the Courthouse officially welcoming Breckenridge into the union—and he came. There was a big party, and the entire event/idea of Breckenridge being left off the map made national news. The "No Man's Land" idea later morphed into a new theme of Breckenridge being referred to as "Colorado's Kingdom", and the theme of the town's independent spirit is still celebrated to today during the annual