The three major stock exchanges in the United States are:

1. New York Stock Exchange (NYSE): The New York Stock Exchange is one of the largest stock exchanges in the United States. It was established in 1792 and supports listings of many large companies across various industries.

2. NASDAQ: NASDAQ focuses on technology companies and growth stocks. It lists companies primarily in e-commerce, software, internet, and other technology-related sectors. NASDAQ is one of the major stock exchanges in the United States alongside the NYSE.

3. NYSE American: NYSE American is a market for small and mid-sized companies, primarily economically advanced companies. It provides opportunities for smaller companies to raise capital, although it is smaller in scale compared to the NYSE.

These three major stock exchanges form the backbone of the U.S. economy and are recognized as significant financial markets globally.