The canary in the coal industry: Home coal delivery

The job: Starting in the second half of the 19th century, coal helped fuel U.S. factory growth as well as many homes with coal furnances. Coal mines were abundant in Midwest states such as Pennsylvania, West Virginia, and Ohio, and railroads made transportation of coal to population hubs easy. Those in the coal delivery business would haul coal from railroad stations to local markets, factories and individual homes.

Killed by: Natural gas and other alternative fuels. In 1940, 54 percent of U.S. households used coal to heat their homes. But according to a report by the U.S. Census Bureau, that number dropped rapidly as fuel oil and natural gas became more widely available. By 1970, just 2.9 percent of the population relied on coal for home heating. Naturally, the number of people delivering coal dwindled as well.

Cures for an ailing industry: Homeopathy

The job: Homeopathy is a system of medicine, founded by German doctor Samuel Hahnemann, at the turn of the 19th century and reached the height of its popularity in the U.S. in the early part of the 20th century. It was based on the idea of treating "like with like." Homeopathists (or homeopaths) treated patients by administering small doses of substances that would in large doses cause symptoms similar to the disease or ailment. For example, small doses of caffeine might be used to treat insomnia or restlessness.

Killed by: Increased standards in U.S. medical education. In 1908, a government study found the quality of American medical schools lacking. And a subsequent report called for stricter admission and graduation requirments. Medical schools across the country, many of them homeopathic, closed as a result. Today, homeopathy remains popular in other parts of the world, including the U.K. and France, and a small number of homeopaths continue to practice in the U.S.