Guano imperialism marked the first major commodity rush into the Pacific. Between 1850 and 1900, the United States claimed over a hundred islands across the world through the Guano Act of 1856. Why did the United States develop a guano empire? Most scholarly attention focuses on state-led explanations for guano imperialism, like the influence of American farmers and naval lobbies on Congress. By contrast, this chapter presents evidence that entrepreneurs led the way into the Pacific. A sudden rise in guano prices led US entrepreneurs to search for guano and threats to their interests from foreign competitors led them to search for government protection.