Chace had previously worked for Samuel Slater, the founder of the first successful textile mill in America. Chace founded his first textile mill in 1806. In 1929, the Valley Falls Company merged with the Berkshire Cotton Manufacturing Company established in 1889, in Adams, Massachusetts. The combined company was known as Berkshire Fine Spinning Associates. In 1955, Berkshire Fine Spinning Associates merged with the Hathaway Manufacturing Company which had been founded in 1888 in New Bedford, Massachusetts by Horatio Hathaway with profits from whaling and the China Trade. Hathaway had been successful in its first decades, but it suffered during a general decline in the textile industry after World War I. At this time, Hathaway was run by Seabury Stanton, whose investment efforts were rewarded with renewed profitability after the Great Depression. After the merger, Berkshire Hathaway had 15 plants employing over 12,000 workers with over $120 million in revenue, and was headquartered in New Bedford. However, seven of those locations were closed by the end of the decade, accompanied by large layoffs. In 1962, Warren Buffett began buying stock in Berkshire Hathaway after noticing a pattern in the price direction of its stock whenever the company closed a mill. Eventually, Buffett acknowledged that the textile business was waning and the company's financial situation was not going to improve. In 1964, Stanton made an oral tender offer of $11 per share for the company to buy back Buffett's shares. Buffett agreed to the deal. A few weeks later, Warren Buffett received the tender offer in writing, but the tender offer was for only $11. Buffett later admitted that this lower, undercutting offer made him angry. Instead of selling at the slightly lower price, Buffett decided to buy more of the stock to take control of the company and fire Stanton (which he did). However, this put Buffett in a situation where he was now the majority owner of a textile business that was failing. Buffett initially maintained Berkshire's core business of textiles, but by 1967, he was expanding into the insurance industry and other investments. Berkshire first ventured into the insurance business with the purchase of National Indemnity Company. In the late 1970s, Berkshire acquired an equity stake in the Government Employees Insurance Company (GEICO), which forms the core of its insurance operations today (and is a major source of capital for Berkshire Hathaway's other investments). In 1985, the last textile operations (Hathaway's historic core) were shut down. In 2010, Buffett claimed that purchasing Berkshire Hathaway was the biggest investment mistake he had ever made, and claimed that it had denied him compounded investment returns of about $200 billion over the subsequent 45 years.