Edward Redmond had no trouble showing a group of about 10 visitors circled around him Wednesday morning the locations of several familiar Southeast landmarks on a map of Capitol Hill: Pete’s Diner, the Starbucks on Pennsylvania Avenue and the Cannon House Office Building.

But Redmond, a Library of Congress cartographic reference specialist, wasn’t looking at a typical tourist map, and his visitors — Capitol Hill residents — had a much more intimate knowledge of the neighborhood than the average tourist. He was examining a 1903 map that detailed the Hill’s streets down to the physical characteristics of the houses on each block, making it easy to identify where modern-day structures would have fit into the city’s grid more than 100 years ago.

This map is just one of the 5.5 million on file at the Library of Congress Geography and Map Division. The Library’s collection of Washington, D.C., maps was featured Wednesday in a talk and tour highlighting the Geography and Map Division’s large collection of intricately detailed folios.

“The strength of our collection is in its comprehensive nature,” said Redmond, who led the program. “A map is not just a picture of the earth’s surface. It is a thematic representation.”

Maps, Redmond added, reflect scientific data, scientific surveying or quantitative analysis, creating a “social snapshot of an area.”

The Sanborn Maps, which were commissioned by insurance companies starting in the 1860s to estimate risk factors and insurance rates in 10,000 cities, document the details of local neighborhoods down to whether the buildings had coal furnaces, which direction the main entrances faced and where the fire hydrants were located on the block.

[IMGCAP(1)]For Capitol Hill residents, the collection can be used to track how the neighborhood has changed over the years.

“Because [the maps were] done in 10-year intervals, we can trace when a porch was added, when a second story was added, when they tore down the house and built a new one,” Redmond said.

Diane Brockett came to the program because she was interested in researching her home on South Carolina Avenue Southeast, a farmhouse that was built before the Capitol was constructed.

“It’s clear this is the place to start,” she said after seeing the Sanborn Maps. “Once you begin to understand what this offers, it becomes a very exciting personal project that you don’t typically think about with maps or the Library of Congress.”

For some, the maps indicated how little has changed over the years. Sylvia Moraes, who lives on Ninth Street Southeast, looked up her address in an 1888 commercial map and found that the basic characteristics of her one-story, wood-frame home hadn’t changed much in the past 120 years.

In addition to the detailed insurance maps, the Library of Congress’ Washington, D.C., collection features rare depictions of the early stages of the city’s construction. Redmond showed the 10 participants on the tour the first published map of the city, which was drawn by Andrew Elicott in 1791, as well as an 1887 facsimile of city planner Pierre L’Enfant’s original 1790 manuscript of the city’s design.

Kay Elsasser, a Library of Congress volunteer who organized the program, said she hopes educational programs led by the division encourage the public to tap into the Library’s resources.

“We want people to know the riches that we have and also to use the collection,” Elsasser said. “The idea is to actually get people to come and do something with this.”

Though the collection has become increasingly digitized over the years, cartography specialists encourage researchers to search in person for the collection’s “gems” whenever possible. No appointment is necessary.

“The Library of Congress is an open public institution and so we encourage people to physically come here and engage,” said Geography and Map Division Chief John Hébert. “We think there are information and resources to be discovered. If anyone says, ‘We’ve discovered it all, we’ve seen it all.’ — forget about it.”

The Library of Congress Geography and Maps Division is located in the James Madison Building at 101 Independence Ave. SE. It is open Monday through Friday, 8:30 a.m. to 5:00 p.m. For more information, visit loc.gov/rr/geogmap.