In 1928, the Dow Jones Industrial Average was expanded to 30 stocks. That total became the familiar modern size of the index, although the individual companies have been replaced many times since then.
The Dow began in 1896 with 12 industrial companies selected by Charles Dow and The Wall Street Journal. It expanded to 20 components in 1916, then reached 30 in 1928, just before the 1929 stock-market crash and the Great Depression. The expansion reflected the growing size and complexity of American industry during the 1920s.
The Dow is a price-weighted index, meaning a stock’s share price affects its influence more than its total market value. This differs from indexes such as the S&P 500, which are weighted by market capitalization. Despite its small membership, the Dow remains one of the world’s best-known indicators of U.S. blue-chip stocks. It is not a complete measure of the entire American market.