From Boom Town to Metropolis: San Francisco

By Luke Carothers

Although San Francisco Mission was founded in the same year of America’s independence in 1776, the community that sprung from this Spanish settlement didn’t officially become part of the United States nearly nine decades later at the end of the Spanish-American War in 1846.  Soon after, the 1849 Gold Rush began, and the small settlement expanded into a busy port.  By the time California was granted statehood two years later, the town’s population exploded from around 1,000 to over 25,000.  In addition to an expanding population to support a gold mining industry, there was also a steady stream of Chinese immigrants moving to the area to work on the Central Pacific Railroad.  A few years later, San Francisco’s population and wealth grew again when gold was discovered in Nevada.  

San Francisco’s location meant that there was a significant amount of infrastructure needed to support a modest population, let alone a growing cosmopolitan port city.  Sitting atop more than 50 hills, surrounded by marshland, the city sits at the end of the San Francisco Peninsula with the eponymous bay on to its east and the Pacific ocean to its west.  San Francisco is also notable for its proximity to both the San Andreas and Hayward Faults, which means the area is highly seismically active.

One of the first major infrastructure projects designed to support the growing population was started and completed in the late 19th century: a system of cable cars that would connect the city’s steepest hills, thus increasing the population’s mobility to different parts of the city.  However, despite this and many other infrastructure and building projects, much of the city was destroyed by an earthquake in 1906.  Luckily, San Francisco’s economic importance and influence meant that the city would be rebuilt quickly and with improvements.  This improvement and the subsequent World’s Fair just nine years later sparked a golden age of improvement in the city, which led to several notable infrastructure projects such as the construction of Treasure island as well as tunnels, reservoirs, and other projects that improved the city’s water supply and supported the population’s mobility.  

However, the most iconic of these projects–the one which has become nearly synonymous with San Francisco itself–is the Golden Gate Bridge.  Spanning nearly two miles across the mouth of the San Francisco Bay, the Golden Gate Bridge is one of the world’s most iconic structures.  The structure is named for the strait it crosses, which opens the San Francisco Bay to the Pacific Ocean.  Likewise, the bridge opens the city of San Francisco to Marin County and a large portion of the surrounding bay.

The need for a bridge spanning the Golden Gate strait was first recognized when gold was discovered in the area, but no serious proposals were started until 1916.  A journalist and former engineering student, James Wilkins, proposed a suspension bridge with a center span of 3,000 feet.  This proposal also came with an unbearable $100 million price tag, but the idea of a suspension bridge with a massive center span sparked the interest of San Francisco’s city engineer Michael O’Shaughnessy who began searching for a similar but less expensive proposal.  O’Shaughnessy soon found Joseph Strauss who proposed an even larger center span–at 4,000 feet–at a fraction of the cost.

Strauss–a poet, engineer, and native Ohioan–revolutionized not only the design of bridges, but also the approach to building them.  In the era of the Golden Gate Bridge’s construction, the injury and death rate of workers was astronomically high, and most large scale projects expected to lose dozens of workers to workplace hazards.  However, Strauss was determined to change the way things were done.  Although Strauss was originally chosen for the project partially due to his ability to shrink the budget, this frugal mindset didn’t apply to the health and safety of the people working on the project.  Strauss required all workers to wear hard hats, making it the first project in the United States to do so.  Additionally, Strauss ordered the construction of a $130,000 movable safety net suspended under the bridge deck.  

During the four years the Golden Gate Bridge was under construction, only 11 workers died as a result of workplace injuries.  This was staggeringly low compared to similar projects such as the San Francisco-Oakland Bay Bridge, which opened 6 months before and lost 28 workers during its construction.  Strauss’ innovations are directly credited with saving the lives of 19 workers who fell but were caught by the safety net.  When the Golden Gate Bridge opened in 1937, it was both the longest and tallest suspension bridge in the world–spanning 4,200 feet in length and 746 feet in height.  The structure is iconic in its scale, design, and aesthetics, but it is equally important for its legacy in safety.  

Projects like the Golden Gate Bridge are emblematic of San Francisco’s importance to the historical development of the United States.  Just as the city’s earliest infrastructure projects laid the groundwork for a growing gold rush, the Golden Gate Bridge laid the groundwork for a new era of construction that pushed the boundaries of what is physically possible while also maintaining a strict standard of safety.  Safety measures such as hard hats and safety netting are now ubiquitous, and Strauss’ legacy has been elevated to new heights with each new safety technology development.

Luke Carothers is the Editor for Civil + Structural Engineer Media. If you want us to cover your project or want to feature your own article, he can be reached at lcarothers@zweiggroup.com.