Santaro Kumagai, the company's founder, began his career as a civil servant in a police department. His construction career started as a stonemason, crafting religious monuments and performing work for the expanding railway network. Kumagai founded his own company in 1898 and incorporated it in 1938. Between 1955 and 1983 the company accounted for more than 10% of all contracts awarded to the fifty-seven members of the Overseas Construction Association of Japan, a figure that outranked the ‘Big Five’ domestic giant construction companies. As overseas projects were riskier, these five companies were reluctant to expand beyond Japan. Kumagai Gumi took advantage of the situation and sought work overseas, as both as a construction company and a developer, using
BOT as project financing, becoming one of the leading proponents of BOT in Southeast Asia. By 1985 overseas earnings amounted to 46% of Kumagai's total contracts. In the 1980s the company became the largest Japanese real estate investor in
New York City, investing in projects in Manhattan, including in projects developed by
William Zeckendorf Jr. ==Major works==