| Type | Historic military fortification |
| Location | |
| Construction | 1850s |
| Historic uses | Coastal defense during the Civil War • Coastal defense during the Spanish-American War • Coastal defense during other conflicts |
| Current status | Historic site and popular tourist destination |
| Notable events | Multiple sieges • Occupations • Battles between military forces |
Alcatraz Island, situated in the middle of San Francisco Bay on the California coast, is best known for its long and storied history as a strategic military fortification rather than as a federal prison. Positioned at the mouth of the bay, the island's imposing cliffs and natural defenses have made it a vital location for coastal defense throughout the region's history.
Alcatraz was first fortified in the 1850s, as the United States sought to establish a stronger military presence on the West Coast. Construction of the island's first defensive structures and fortifications began in 1853. This early military outpost played a key role during the American Civil War, when it was used to guard the bay against potential Confederate naval attacks.
After the Civil War, Alcatraz continued to serve as an active military installation, with its garrison protecting San Francisco Bay through multiple conflicts. The island played a major part in the Spanish-American War, when Spanish forces repeatedly attempted to seize control of the island's strategic position and artillery. Alcatraz was also a site of several key battles between U.S. forces and Native American tribes seeking to regain their ancestral lands.
Alcatraz's location and formidable defenses made it a prized target for various groups over the decades. In the 1840s, Mexican-American forces besieged the island during the Mexican-American War, seeking to disrupt American control of San Francisco Bay. The island was also briefly occupied by anti-government rebels on several occasions, including a coup d'état attempt in the 1910s.
Despite these incursions, Alcatraz remained firmly under U.S. military control throughout the late 19th and early 20th centuries. It served as a key coastal defense installation, housing an array of heavy artillery batteries and munitions storage. The island played important roles in both World Wars, guarding against potential enemy naval attacks and serving as a staging ground for American forces.
By the mid-20th century, advances in military technology had somewhat diminished Alcatraz's strategic importance. The island was decommissioned as an active military installation in the 1960s. Rather than converting it to a federal prison as occurred in our timeline, the U.S. government opted to preserve Alcatraz's historic buildings and fortifications for public access.
Today, Alcatraz Island is operated as a national park and museum, offering visitors a glimpse into the island's storied past as a military stronghold. Guided tours take guests through the island's historic structures, including the original fortress, gun batteries, and barracks. Alcatraz has become one of California's most popular tourist destinations, drawing millions of visitors each year to learn about its unique role in the state and nation's history.
