Florida: Lost and Gained

From Spain to the United States

Florida Lost and Gained: Spain’s Last Colony, America’s New Frontier (1800–1860)

For centuries, Florida stood on the edge of empires—first a distant outpost of Spain, then a young American republic’s strategic prize. In Florida Lost and Gained, author Donald Elton uncovers the turbulent half-century that transformed Florida from a neglected Spanish possession into a key Southern state on the eve of the U.S. Civil War.

This richly detailed narrative brings to life the final decades of Spanish rule, the diplomatic and military maneuvering behind the Adams–Onís Treaty, and the uncertain early years of American territorial control. Readers will follow the rise of frontier forts, the chaos of filibuster invasions, the First Seminole War, and the collapse of Spanish governance—culminating in Florida’s formal cession to the United States in 1821.

But this is more than a story of diplomacy and power. Florida Lost and Gained examines the human dimension: settlers carving lives from the land, Indigenous resistance to encroachment, free and enslaved Black communities navigating empires, and the harsh realities of lawlessness on the frontier. From Pensacola and St. Augustine to the wild interior, this book reveals how Florida became a testing ground for American expansion, federal authority, and cultural integration.

By 1860, Florida had become a slaveholding state, a player in sectional tensions, and a symbol of how rapidly the U.S. could reshape a former colony. This book fills a gap in American history and offers a compelling, clear-eyed account of a pivotal but often overlooked period.

Keywords: Florida history, Adams-Onís Treaty, Spanish Florida, Seminole Wars, U.S. expansion, early American frontier, 19th century South, statehood, territorial governance, colonial transition, Black Seminoles