A student of Frederick Jackson Turner, Bolton disagreed with his mentor's Frontier theory and argued that the history of the Americas is best understood by taking a holistic view and trying to understand the ways that the different colonial and precolonial contexts have interacted to produce the modern United States.

The height of his career was spent at the University of California, Berkeley where he served as chair of the history department for twenty-two years and is widely credited with making the renowned Bancroft Library the preeminent research center it is today.

Starting in 1897, Bolton was a Harrison Fellow at the University of Pennsylvania and studied American history under John Bach McMaster.

In his book The Americas, George P. Hammond noted, “the next twenty years might well be called the Bolton era in historical studies at the University of California.” In his dual capacity as founding director and chairperson, he made Bancroft Library a great research center for American history and elevated his department into a top-ranking position in the historical world.

His round-table seminar became famous, and the historians trained in that group have long been known as the “Bolton School.”[2] At Berkeley he supervised more than 300 Masters theses and 104 doctoral dissertations, an all-time record.

A year later, Bolton published Texas in the Middle Eighteenth Century: Studies in Spanish Colonial History and Administration.

Over the next twenty-nine years, Bolton published many works, including Texas in the Middle Eighteenth Century (1921), The Spanish Borderlands (1921), Outpost of Empire (1931), Rim of Christendom (1936) and Coronado (1949), for which he received a Bancroft Prize from Columbia University.

Portland State University archaeologist, Melissa Darby, maintained Bolton knew it was a forgery but took part in a deliberate deception to support his contention that Drake landed somewhere near San Francisco Bay.

[6] His doctoral students include Woodrow Borah, John W. Caughey, LeRoy R. Hafen, Abraham P. Nasatir, J. Fred Rippy, and Ursula Lamb.

Biographer Kathleen Egan Chamberlain argues: His writings, particularly The Spanish Borderlands, still challenge traditional views of colonial and frontier history.

The search for common historical elements between North and South America remains an open subject, and the call for greater hemispheric history has yet to be answered.