The Dow Jones Industrial Average (Ticker:^DJI) is one of several stock market indices created by Wall Street Journal editor and Dow Jones & Company co-founder Charles Dow. Dow compiled the index as a way to gauge the performance of the industrial component of America’s stock markets. It is the oldest continuing U.S. market index, aside from the Dow Jones Transportation Average, which Dow also created.
First published on May 26, 1896, the DJIA represented the average of twelve stocks from various important American industries. Of those original twelve, only General Electric remains part of the average.
Today, the average consists of 30 of the largest and most widely held public companies in the United States. The "industrial" portion of the name is largely historical—many of the 30 modern components have little to do with heavy industry. To compensate for the effects of stock splits and other adjustments, it is currently a scaled average, not the actual average of the prices of its component stocks—the sum of the component prices is divided by a divisor, which changes over time, to generate the value of the index. (From Wikipedia)