The Iowa state ban on the use of thimerosal in almost all vaccines used on children became effective. Iowa, passed the law on 14 Apr 2004, and became the first state in the U.S. to enact such restriction. California followed in 26 Aug 2004. State politicians reacted to public concern. Thimerosal contains ethylmercury, a compound of mercury. In other circumstances, mercury is known to be a toxic substance. However, thimerosal had been used in microgram quantities in vaccines to prevent bacterial contamination since the 1930s. On 9 Jul 1999, the Centers for Disease Control and Prevention and the American Academy of Pediatrics, merely as a precaution, asked pharmaceutical companies to discontinue its use in vaccines as soon as possible, though medical evidence was otherwise reassuring.«

English inventor Andrew Smith Hallidie, in the U.S. since 1852, revolutionized transportation methods in San Francisco when he successfully tested a cable car he had designed to solve the problem of providing mass transit up San Francisco's steep hills. He not only invented, but also manufactured, and patented the first cable car and its system of wire ropes, pulleys, tracks, and grips that made it possible. Hallidie, an engineer and one-time miner, realized the need on one foggy day in 1869 when he watched in horror as horses pulling a carriage up one of the City's steep grades slipped on the wet cobblestoned street, the heavy carriage rolled backward downhill and the five horses dragged behind it suffered fatal injuries. Hallidie, using wire rope, had already had much success in the use of cable drawn ore cars for use in mines.