When Chris Olsen first saw the historic plat maps in the University of Pittsburgh's digital research library, the 32-year-old geographer in Redlands, Calif., got an idea.
His job in tech support for Esri -- a geographic information systems software company -- is to help clients solve mapping overlay problems. He thought that if he used the Pittsburgh maps to solve some of the same problems, he could help his clients by sharing his experience. Though inspired by his interest in history and a connection to Pittsburgh -- his wife is a Pitt graduate whom he married in Heinz Chapel -- it was meant to be a work tool.
Then a colleague of his blogged proudly about it, and in recent weeks, Mr. Olsen's moving, zooming, time-traveling map has become a bit of a local sensation.
"Pittsburgh Mapping and Historical Site Viewer" -- http://peoplemaps.esri.com/pittviewer/ -- popped up on someone's Facebook page, then spread. Jonathon Denson of McKees Rocks described it as "an awesome mapping tool" on his Discovering Historic Pittsburgh website. Someone then posted it on City-Data.com, where Gene Wilson of Allegheny West found it.
"I'm going to waste a lot of time exploring this thing," he commented.
Not before he put it on a North Side chat site.
"I adore this map site, mostly because it provokes further looking around," wrote Eileen Byrnes of Marshall-Shadeland, who saw it on the chat site. "I've got a crazy love for trolleys and was thrilled to learn there was a trolley on Superior Avenue, my street, in 1902."
To create the viewer, Mr. Olsen downloaded and scanned the historic plat maps of the years that were available and spliced them to create one map of Pittsburgh and Allegheny City in eight overlays. The user can zoom in and use a time line to see overlays for 1835, 1855, 1872, 1882, 1903-07, 1910, 1923 and 2010, an aerial view.
Symbols on the map are links to information boxes, usually with a photo, about historic sites.
"I am a big fan of history and looking at historical maps was always fun for me," said Mr. Olsen, who credited the ArcGIS software for doing the hard part. "When I stumbled across the [Pitt] site, I thought, 'This is great,' but you had to go to different plats. They were organized well, but the challenge was to get them to all fit together."
There are gaps, blank blotches and some streets that don't line up. Some overlays are distorted in zoom. Others come into focus by using the timeline like an old radio dial. But it's fascinating to purposefully blur between 1923 and 2010 to see at the same time today's highways and the imprint of the grids they replaced.
The decades of 1872 and 1882 marked several dramatic transformations as the city grew.
One was in Lawrenceville, where a large triangular green space in the neighborhood seemed to have been a placeholder for development.
Called Iron City Park on the 1872 map, its western foot is the Frauheim and Vilsack Brewery (later the Iron City Brewery) and the eastern foot stretched to 39th Street. The point north reached almost to Penn Avenue. Liberty Avenue went around it.
Within the green shading, a historic symbol represents the former St. John the Baptist Catholic Church, now the Church Brew Works. On the 1882 map, the green space is gone, Liberty cuts through and Woolslayer, Mintwood, Cabinet and Clement have filled in the grid.
The site of the Connelley School on Bedford Avenue was a basin where the city had its waterworks in 1872. Central High School was on the site, too. In 1903-07, the site was Washington Park, which it was in 1923. When you nudge the timeline to 2010, it's noodles of highway.
Mr. Wilson, whose first reaction to the viewer had been "wow," said he was particularly interested in seeing how Chateau, where he works, had changed. Chateau was once part of Manchester.
"It's sad to see so clearly how areas like Chateau and the area by the 16th Street Bridge used to be such vibrant areas and are now gone," he said.
Between the 16th Street Bridge and the Interstate 279 interchange on the North Shore south of the railroad tracks was a community of Swiss immigrants, which Mr. Denson describes on his web site with photographs of what is left. The dense street grid is vaguely visible in 1855 and becomes clearer as you drag through the decades until 2010, whose aerial view is block after block of pavement.
Mr. Denson said the map has "excited a lot of interest among us history nerds. It makes it easier to date buildings and compare changes in the built environment. Chris Olsen has done a tremendous service to building historians and others interested in the way modern development has impacted the urban fabric."
Mr. Olsen said he was most interested "in seeing how things change over time. I have always been interested in what was where, and unless you had a viewer like this it was a challenge. "I'd kind of hoped people would say 'That's cool,' but I didn't know how popular it might become or how it would be used.
"Now I can imagine a myriad of things you can do with it."