Berkshire Hathaway is the company founded in 1839 that owns GEICO and BNSF Railway and ranks among the largest by market capitalization.
The business began as a textile manufacturer in New England. Warren Buffett and his investment partners acquired shares in the 1960s, and Berkshire gradually shifted away from textiles toward insurance, investments, and wholly owned operating companies.
Berkshire's insurance businesses include GEICO and reinsurance operations. Its non-insurance holdings include BNSF Railway, Berkshire Hathaway Energy, and numerous consumer and industrial companies. The diversified structure helps explain why its market value is not tied to a single product.
The company is associated with Buffett, but Berkshire Hathaway is not simply an investment fund. It is a publicly traded holding company with operating subsidiaries and a large portfolio of marketable securities.