Despite these conflicts, Frémont did make the important observation that Alcatraz was strategically positioned to be a premier military fortification for the protection of San Francisco. Shortly after the signing of the peace treaty with Mexico in February of 1848, the United States Military took notice of the Rock and its strategic value as a military fortress. First Lieutenant William Horace Warner of the Corps of Topographical Engineers had begun conducting geological surveys on Alcatraz a year earlier in May of 1847. Warner was stationed out of Monterey under the command of Brigadier General Stephen Watts Kearny, who had been in the forefront of the dispute over Stockton’s appointment of Frémont as Governor.
Lieutenant William Warner’s 1847 Survey Map of Alcatraz.
The Gold Rush
The discovery of gold in Coloma California in 1848 caused a worldwide frenzy and families from around the globe journeyed to the region with dreams of striking it rich. The population of San Francisco surged from four hundred in 1848 to thirty thousand by late 1849.
The California Gold Rush is remembered as an extraordinary episode in San Francisco’s colorful history and it also influenced the government to find the means of protecting its land claims from other powers. On a cold and crisp morning on January 24, 1848, mill carpenter James Marshall walked down a steep path to a river clearing where his crew was building a mill for John Sutter. Marshall wrote of what followed:
One morning in January – it was a clear, cold morning, I shall never forget that morning – as I was taking my usual walk along the river after shutting off the water, my eye was caught with the glimpse of something shining in the bottom of the ditch. There was about a foot of water running then. I reached my hand down and picked it up. It made my heart thump, for I was certain it was gold!
The tiny nuggets that Marshall had found that morning in Coloma, California had little value – their total worth was less than fifty cents. But Marshall’s discovery would change California history. Marshall’s find at Sutter’s Mill stirred little excitement from local newspapers and it was a Coloma general store owner named Sam Brannan who would become the mastermind behind the gold frenzy. Marshall told Sam about his find, and soon Brannan had collected several nuggets that he gathered into a small medicine bottle. Riding horseback into San Francisco along old Montgomery Street, he shouted to passing patrons, announcing his gold find in the American River. In January of 1848 the entire population of San Francisco was less than four hundred, but by the following year the populace would explode to over thirty-thousand and Brannan would become exceptionally wealthy from selling mining equipment to the new settlers.
As word spread around the globe of abundant riches in California, the United States Government would evoke security measures to protect its land and mineral resources from seizure by other countries. San Francisco developed into a principle port of U.S. commerce, second only to New York’s grand harbor. The incentive to safeguard San Francisco using the United States Military had now become a key priority. A commission was appointed to select sites for military fortifications, and Alcatraz seemed to be a strategic gift from nature.
A bird’s-eye view of the City of San Francisco, rendered in 1868. Alcatraz Island is clearly visible at the center of the bay with a dense crowd of vessels congregating at the city’s eastern crest.
By 1849, the Port of San Francisco had become tremendously active. Establishing a lighthouse became an immediate priority, to help ships navigate into the new western shipping harbor. Since the military had not yet begun development of the island into the promising military fortress that it would become, the construction of the first western lighthouse was contracted to a Baltimore firm. The crew arrived in San Francisco on January 29, 1853 and immediately began work. The design was for a Cape Cod style two-story cottage with a central light tower and the fifty-foot lighthouse was to be painted white with black trim. The fixed third-order lens did not arrive until October of 1853, and budget problems would delay its installation until June 1, 1854. A fog bell would be added in 1856, after it became clear that frequent fog layers often rendered the light ineffective. The original fog bell had to be rung by hand, but later versions were equipped with a clockwork mechanism that automatically struck the bell at prescribed intervals. As the city of San Francisco continued to grow, a new flashing fourth-order lens was installed, which aided mariners in distinguishing the lighthouse from the city lights.
Alcatraz was the site of the first lighthouse on the Pacific Coast, which commenced operation on June 1, 1854. The structure featured a Cape-Cod-style two-story cottage with a central light tower. The optical lens concentrated the luminance from the flame of a whale-oil lamp into a powerful beacon that could be seen from nearly twenty nautical miles out at sea. The small signpost visible next to the planter indicates that this building also served as a post office.
A full view of the original lighthouse, surrounded by the fort’s arsenal of cannonballs. A close study shows what appear to be children and their mother (left) sitting atop the pile of fifteen-inch cannon balls, each of which weighed over four hundred pounds. Also visible (far left) is the post headquarters.
An early San Francisco defense map drawn in 1863 shows cannon firing ranges from various strategic locations. As the port and city of San Francisco continued to flourish, the military established a concentrated system of fortifications to protect the prosperous settlement. Clearly visible is the triangular defense pattern, which was anchored by the strategically located Alcatraz. Hostile ships entering the harbor would first come under fire from both Lime Point and Fort Point, and would eventually progress into the operative firing range of all three positions. It was an effective and lethal schematic.
On November 1, 1850, a joint Army-Navy military commission presented a report detailing a military defense plan to guard San Francisco from unfriendly powers. Their report stated: “The first consideration in conjunction with defense would be to prevent the passage of hostile vessels through the channel of entrance.” This would be achieved by creating two lines of defense:
“The outer one at the Golden Gate to consist of a fortress at Fort Point of one hundred and fifteen guns and a battery of one hundred guns directly opposite on Lime Point; the inner to consist of a fortress at Alcatraz with batteries at Black Point (now Fort Mason), and Angel Island.”
The aim was to create a gauntlet of cross fire, which could pour down a continuous barrage of shell all the way from Point Lobos to Telegraph Hill, a distance of about seven and a half miles – which no vessel of the day could survive. In its report, the commission urged immediate development of the fortresses to solidify authority and enhance protection of the infant U.S. territory.