Alcatraz Island's Construction Timeline Alcatraz, the infamous island prison in San Francisco Bay, began its transformation from a rocky outcrop into a fortified site in the mid-19th century. Initially spotted by Spanish explorer Juan Manuel de Ayala in 1775 and named "La Isla de los Alcatraces" for its pelican population, it wasn't developed until U.S. military needs arose during the California Gold Rush.

Military Fortress Phase (1850s) Construction kicked off in 1850 when President Millard Fillmore reserved the island for defense, amid booming San Francisco growth. The U.S. Army Corps of Engineers started building in 1853, erecting a lighthouse (lit in 1854, the first on the Pacific Coast), fortifications, and a military prison by 1858. About 200 soldiers garrisoned there initially to guard the bay.

  • Key early structures: Bomb-proof barracks (1865-1867) with 10-foot-thick brick walls.
  • Citadel demolition later made way for expansions.

Shift to Prison Era (1900s-1910s) By 1907, Alcatraz fully transitioned to the Pacific Branch U.S. Military Prison due to overcrowding from the Spanish- American War. Major Reuben Turner's massive concrete cell block—once the world's largest—began construction in 1909 and finished in 1912, housing prisoners who built it. The original lighthouse was replaced that same year with an 84-foot tower still standing today.

Federal Penitentiary Opening It became a federal prison on August 11, 1934, welcoming notorious inmates like Al Capone, but operated only until 1963 due to high costs and decay. Today, it's a National Park drawing 1.5 million visitors yearly for tours of its haunting history.

Phase| Start Year| Key Builder/Event| Purpose
---|---|---|---
Fortress| 1853| Army Corps of Engineers| Bay defense, lighthouse
Military Prison| 1907| U.S. Military| Incarceration post-war
Cell Block| 1909-1912| Major Reuben Turner| Main concrete structure
Federal Era| 1934| Bureau of Prisons| "Escape-proof" for worst offenders 135

Modern Legacy and Visits Now part of the Golden Gate National Recreation Area, Alcatraz symbolizes resilience—from Native American occupation (1969-1971) to eco-habitat for birds. No major recent developments as of February 2026, but tours highlight its architecture and wildlife exhibits. Imagine standing in those cold cells, hearing echoes of failed escapes—its story endures.

TL;DR : Alcatraz's core military build was 1853-1858; iconic cell house 1909-1912; federal prison opened 1934.

Information gathered from public forums or data available on the internet and portrayed here.