On April 27, 1813, the British commander of Fort York, then a remote colonial outpost, ordered his troops to detonate a building packed with gunpowder in an attempt to distract the advancing American forces. The massive explosion of the so-called Grand Magazine could be heard for miles and killed several soldiers.

Apparently, the reverberations were still faintly audible as recently as this past March, when Toronto resident Nathan Ng decided to post a question on the fort's Facebook page, asking about the exact location of the storied blast.

Mr. Ng is a 40-year-old tech manager who grew up in Kitchener and has lived here for about 15 years. He describes himself as "a Toronto enthusiast." "The question," he recalled recently, "got back to Steve Otto and he sent me a note."

Story continues below advertisement

Mr. Otto, the 73-year-old founder of the Friends of Fort York, is the pre-eminent expert on the city's architectural heritage. The crater, he explained to Mr. Ng, was just outside the southern ramparts, and is denoted on maps of the fort.

The question, however, didn't end with the answer. Indeed, the serendipity of their social network exchange brought Mr. Otto and Mr. Ng together on a thoroughly 21st-century collaboration, which seeks to make the fort's rich, but largely paper-based, mapping legacy readily available to the citizen historians who trawl the Web.

Their recently launched website, fortyorkmaps.blogspot.ca, has almost 60 pages of maps of the fort and the properties situated on the surrounding military reserves, later known as "the liberties." "We're trying to trace [the fort's] history through historical maps," says Mr. Ng. "Some had not been digitized before."

Serving up history as a captivating cartographic mash-up, the website vividly illustrates how a rapidly industrializing city nosed its way up to the very walls of the garrison, finally choking it off with landfill, industry and transportation infrastructure that almost included, at one point, a proposed streetcar that would run directly through the middle of the fort.

Flipping through the maps is almost like watching an accelerated stop-motion video documenting the waterfront's long march from forested outpost to manufacturing hub to high-rise haven. In fact, the site includes contemporary land-use planning diagrams and architectural renderings of as yet unbuilt developments.

The scanned maps also offer fascinating clues about the often forgotten historic linkages between Fort York and the Canadian National Exhibition (site of the "new fort," the only remnant of which is the Stanley Barracks), the "lunatic asylum" (now the Centre for Addiction and Mental Health on Queen West) and Victoria Square, the location of the garrison's original burial ground and currently a quiet park in the midst of the King West condo neighbourhood.

Mr. Otto and Mr. Ng are a somewhat unlikely duo in this endeavour. In the 1970s, Mr. Otto headed up the Ontario government's heritage services division, and came to public view as editor of architect Eric Arthur's No Mean City, a broadside against Toronto's postwar campaign to demolish its Victorian heritage.

Story continues below advertisement

Since the late 1990s, he's been waging a remarkably successful war with downtown developers, the city and even the TTC to ensure that the fort – which has endured several near-death experiences at the hands of public officials – survived to see the bicentennial of the War of 1812.

About a dozen years ago, he even persuaded then mayor Mel Lastman to cut a deal to reclaim a few acres of land from railway companies that used to belonged to the fort.

For his part, Mr. Ng, who once lived in a basement apartment on Niagara Street not far from the fort's northern ramparts, became intrigued by the area's rich heritage in a very different way. For several years, he belonged to a climbing club housed in a 19th-century industrial building near Bathurst and Front. When the owners sold the land and demolished the structure, he was outraged, and decided to learn more about the factory's history.

That query led to their first exchange, as Mr. Otto, who is well known in Toronto historical circles for his encyclopedic knowledge of the city's older buildings, offered some tips on how Mr. Ng could pursue his research.

His appetite whetted, Mr. Ng embarked on his digital mapping projects – two non-commercial, DIY websites that contain hundreds of scanned historic Toronto maps, including the spectacular pink and yellow Goad's fire insurance maps.

Mr. Ng is enthralled by both the content and the aesthetics of old maps, surveys and the bird's eye view drawings that were popular with Victorians. "I think the maps are incredibly powerful because there are two levels of subjectivity to them," he observes. "They're an abstraction of what the mapmaker thought was important. [But] sometimes what's left out is just as important as what's put in."

Story continues below advertisement

He also sees old maps as a trigger to the historical imagination: "You look at a map and close your eyes and try to figure out how it relates to the real world. Oftentimes, a building doesn't exist any more. What was it? Why is it gone? [The map] leads to a whole host of questions."

Mr. Otto, a professional historian, served as the expert adviser, pointing Mr. Ng to various archival collections and providing the contextual analysis around the images. The Friends of Fort York, he hastens to add, didn't have anyone with Mr. Ng's technical abilities. "He brought to the table skills that I don't have."

In Mr. Otto's view, the project offers a way of connecting the painstaking and dusty work of archival research to a mass audience, and especially a younger generation compelled by digital images. "Maybe you have to bring the stuff out of the archives to the point of interface with the broader public," he muses. "You put them where people will find them and hope it feeds their interest going forward."

Mr. Ng's two previous online map collections can be found at goadstoronto.blogspot.ca and oldtorontomaps.blogspot.ca.