Using high-definition sonar, researchers have located and mapped the remains of the SS City of Rio de Janeiro, a steamship that quickly sank on a fog-shrouded morning in 1901 after running aground near the present-day Golden Gate Bridge. Only 82 of the 210 passengers and crewmembers onboard survived the disaster, prompting some historians to dub it the “Titanic of the Golden Gate.” Most of the victims were Chinese and Japanese immigrants just a stone’s throw away from their new lives. The discovery of the long-lost City of Rio, announced on Wednesday, comes in the midst of a two-year government effort to document shipwrecks in the Bay Area.

Built in 1878, the 345-foot SS City of Rio de Janeiro spent its early years going back and forth between Brazil and the United States. But when this proved unprofitable, it was sold and re-pressed into service moving goods and passengers across the Pacific Ocean. For two decades the City of Rio followed the same route—Hong Kong to Japan to Hawaii to San Francisco—except for a brief period in which it served as a troop transport during the Spanish-American War. In 1890 it suffered extensive damage upon colliding with another ship in Hong Kong’s harbor. Five years later it hit a reef off the coast of Japan, and in 1897 it got caught in a vicious typhoon. Yet it had never lost a single passenger.

On its ill-fated last voyage, the City of Rio found itself a few days behind schedule as a result of bad weather and mechanical difficulties. It finally reached the California coast on February 21, 1901, only for a thick fog to prevent it from advancing the last few miles into port. That night over dinner, the ship’s most prominent passenger, Rounsevelle Wildman, a top U.S. diplomat based in Hong Kong, purportedly pressured the captain to hurry along so that he could catch the train to President William McKinley’s second-term inauguration in Washington, D.C. The captain also apparently had a social engagement he didn’t want to miss. Whether influenced by these factors or not, the ship’s crew raised anchor around 4 a.m. the following day. But although the fog had cleared momentarily, it soon drifted back in, reducing visibility to near zero.

In these poor conditions, the City of Rio veered too far south as it entered the Golden Gate, a treacherous strait connecting San Francisco Bay and the Pacific Ocean (now spanned by the Golden Gate Bridge). At about 5:30 a.m., while most passengers slept in their cabins below, it collided with jagged rocks off of San Francisco’s Fort Point, ripping a huge gash in its iron hull. Frigid water quickly rushed in as the tide pushed the ship off the rocks, and within 10 minutes it had gone under. American officers and Chinese crewmembers attempted to whisk everyone up on deck and get them into lifeboats, but they were hindered by the language barrier between them. In the end, only a couple of lifeboats launched successfully, whereas other passengers clung desperately to debris. Hearing the ship’s distress calls, fishermen rushed to the area and rescued as many people as they could. But 128 perished anyway, including Wildman, his wife and his two children, along with about 80 Chinese immigrants and additional immigrants from Japan.

The shipwreck attracted the attention of newspapers around the world and remains well known in the Bay Area. “I grew up out here, and that’s a story you were told rather early on in your life,” said James Delgado, director of maritime heritage for the National Oceanic and Atmospheric Administration’s Office of National Marine Sanctuaries. “It was the worst disaster of the Gate.” Wreckage from the City of Rio continued popping up for years afterward, such as a wooden barrel found in 1917. But although many people tried, largely due to rumors about silver bars onboard, no one could locate the ship itself. A man claimed to have come across it in 1931 with a tiny homemade submarine, but he never resurfaced from a later voyage. Delgado explained that the waters of the Golden Gate are deep, dark and extremely fast moving, with lots of shipping traffic. Looking for the City of Rio through a mask or with a remote-control camera, he said, is like “trying to get a glimpse of something with a flashlight in the middle of the night in a driving snowstorm.”

Sonar, on the other hand, is a much more effective search tool, and in 1987 commercial explorers used it to find what they believed was the wreck. However, they were unable to reach it by the time their permit to salvage expired a few years later. Even if they had, Delgado stated, they would have discovered tin instead if the silver they expected. Plus, he said, they would have been “digging through what is a grave.” Delgado believes that the commercial group did, in fact, find the City of Rio. But it’s hard to tell for sure, he said, because the coordinates they gave did not match up with records at the National Oceanic and Atmospheric Administration (NOAA), a federal government agency that, among other things, charts the seafloor.

Recently, NOAA began its own search for the City of Rio as part of a two-year project to document the roughly 200 shipwrecks in and around the Golden Gate National Recreation Area and the Gulf of the Farallones National Marine Sanctuary. First, it partnered with sonar expert Gary Fabian, who pinpointed the mud-covered remains in 287 feet of water. (The stern had broken off and was even deeper.) NOAA did not have a submersible capable of getting down there. So it again looked outside the agency, with private companies donating a research vessel, a crew and a remotely operated vehicle equipped with high-definition 3-D sonar technology. “The ROV is bigger than a refrigerator, and it weighs a ton and a half,” Delgado explained. One day in early November, the crew lowered this behemoth off its boat and began mapping the City of Rio. It also mapped the nearby SS City of Chester, which had gone down in 1888.

By locating such shipwrecks, researchers provide closure for grieving families, according to Delgado, who added that they bring to light “powerful human stories, like those of immigration and loss, perseverance and bravery.” NOAA also assess whether any of the ships pose an environmental risk. Corroding fuel tanks, for example, could hypothetically be poised to burst, with negative consequences for the sensitive marine ecosystem. At the same time, scientists can study the animals living in what are now essentially artificial reefs. “We need to pay more attention to the ocean,” Delgado said. “It’s 70 percent of the planet. And it’s 70 percent of the planet that happens to contribute half of the food we eat.”