Until 1935, the taxi industry in New York was comprised of unregulated companies fighting for dominance. This all changed during the Great Depression. Widespread poverty prompted many New Yorkers to opt for less-expensive forms of transportation, decreasing the demand for taxis. This put many companies out of business and caused many cabdrivers to lose their jobs. The situation was made worse by the tactics of “wildcat” (unlicensed) taxis who used what some considered to be “underhanded tactics,” such as drastically lowering fares, to get more business.

1954 Checker A6. Photo courtesy of Coachbuilt.com
  The situation in the taxi industry was dire; frustrated cabdrivers turned their anger into violent protest and the demands for industry regulation increased. While regulation had already existed in some form with the Bureau of Licenses (aka the Police Department's “Hack Bureau”), many New Yorkers claimed that it was not enough. New York City's Board of Aldermen (the predecessor of the modern New York City Council), responded to calls for reform in 1937 by passing the Haas Act. The Haas Act established the medallion system for New York taxicabs, which is still in use today. The Act's provisions included a limitation on the number of "medallion" licenses (and therefore, taxicabs) to the number that existed at the time. This number would be further reduced through attrition. As anticipated, this brought the supply of taxicabs closer to the level of service the public demanded, thus calming the fierce competition for customers. The stability the Haas Act brought to the taxi industry laid the foundation for the later successes of the war and post-war years.
A confluence of post-Depression events helped the taxi industry in New York thrive. Facing the rationing of fuel and car parts during World War II, many turned to taxis for transportation. The resulting jump in demand helped the taxi industry grow, as drivers no longer had to fight for business. Meanwhile, the value of medallions increased exponentially once license holders realized that they were indeed a transferable asset somewhat like real estate. While licenses cost $10 in 1937, medallions traded for an average $5,000 dollars in 1950. The profile of taxicab drivers also changed, with an increase in women and African American drivers in the industry during and after the War.
1959 Checker A92. Photo courtesy of Coachbuilt.com

During this period, several aspects of the modern-day taxi began to emerge, such as the popularity of the comfortable and stylish Checker taxicab. Checkers were immensely popular in the 1940s and 1960s and are considered an iconic part of vintage New York history. Perhaps more importantly, the relationship between cabdriver and passenger began to take a more familiar shape. Cabdrivers no longer were thought of as people of dubious character, but instead were perceived as “an oracle, a counselor, a philosopher and an almanac," as Professor Graham Russell Gao Hodges wrote in his book, “Taxi! A Social History of the New York City Cabdriver”. Cabdrivers were seen as sources of advice and as experts on New York, an image bolstered by numerous movies and radio shows of the era. On occasion, cabbies were even seen as heroes who returned lost items and helped deliver babies.

(l to r) 1938 Checker. Photo courtesy of Coachbuilt.com; 1941 Checker M. Photo courtesy of Coachbuilt.com; 1939 Checker M4. Photo courtesy of Coachbuilt.com