San Francisco is connected to the North and East bays by two vast, famous bridges. But before the Golden Gate Bridge ever tethered Marin to the Presidio, and the very same year work on the Bay Bridge broke ground, a smaller, multi-functional little drawbridge was built. The Third Street Bridge opened in 1933, to connect Mission Bay to SoMa. Today, in spite of its heft and almost comically industrial appearance, it remains a vital piece of infrastructure adjacent to bustling AT&T Park.

At around 250 feet long, it’s not a huge bridge, but it’s a remarkable feat of engineering. Designed by Joseph Baerman Strauss, who also drafted plans for the Golden Gate Bridge, it’s called a “single-leaf bascule bridge.” Its span lifts up and lowers in a speedy three minutes, thanks to a counterweight on the AT&T Park side of Mission Creek. In the mid-1900s, it carried trains and streetcars, shuffling workers and supplies to and from the busy shipyard and canneries that dotted the Bay-side of San Francisco.

The bridge got its contemporary moniker in 1969, when it was renamed the Lefty O’Doul Bridge after the baseball player who was born in the Bayview. Today, it contains five vehicle traffic lanes and two wooden walkways on either side, which shake when cars drive past, giving pedestrians an odd sense of vertigo. But 85 years into its job, it’s going strong. In modern times, only around 400 sea vessels per year request to pass underneath, but as one of only four drawbridges in San Francisco, it’s still considered pretty special; the city’s Planning Department named it a landmark in 1989.

But it’s not the only historically significant bridge in the area; one block away is the Fourth Street Bridge, which deserves a shoutout. Also designed by Strauss, but built 15 years before its counterpart, it carries the KT-Third Street’s light-rail trains along with auto traffic. It’s also been declared a landmark, which made for a bizarre renovation challenge several years ago: Its massive cement counterweight, deemed no longer useful but still historically important, was recreated in fiberglass at the cost of some $400,000, to maintain its industrial appearance.

Both bridges remain functional today, but it’s easy to forget their history when walking from the parking lot to AT&T Park for a Giants game. But next time you do, take a closer look at the massive steel beams and impeccable design, which has created an important pathway to Mission Bay for nearly a century.

Read more from SF Weekly‘s Mission Bay issue:

Mission Bay: The Most Misunderstood Neighborhood

What do you make of a place whose crowning aesthetic achievement is a 10-story parking garage?

What’s It Like to Live on a Houseboat in Mission Creek

Please don’t change the channel, this tight-knit neighborhood of 20 houseboats asks. But Mission Bay is on the move.

Mission Bay Has More Parks Than You Think

In a rare push for green spaces, 40 acres of parks are planned for residents of the 6,400 new housing units in Mission Bay.

Bio Companies Are at the Root of Mission Bay’s Growth

Before the Golden State Warriors staked claim on Mission Bay with a new arena, biotechnology companies and healthcare providers spent two decades turning it into a medical hub.

The 10 Best Places to Eat and Drink in Mission Bay

Food trucks and fine dining in a neighborhood that doesn’t always get a lot of love.