Types. Economists Ronald G. Ehrenberg and Robert Smith, authors of Modern Labor Economics, identify two main types of labor unions: craft unions and industrial unions. Craft unions represent workers in a specific occupation.lthough union membership in the United States peaked in the mid-20th century and has declined since then, various types of labor unions remain an influential force in American business and politics.
U.S. Army Physicians Discovered the Cause of Yellow Fever. August 27, 1900. No one knew what caused the often-deadly yellow fever, but it occurred in epidemic proportions, with one person after another in a given area becoming sick. People feared the mysterious disease, until U.S. Army physician James Carroll endangered his own health in the name of science.
The first definitive evidence of yellow fever in the Americas was in Mayan manuscripts describing. an outbreak of the disease in the Yucatan and Guadeloupe. 1668-1699 Outbreaks were reported on the eastern coast of the United States , including in New York (1668), Boston (1691), and Charleston (1699). 1700s.