It’s a modern miracle: Plug an address into your favorite Internet map site and pull up a picture of what’s there. But what if you could turn back the clock 50, 100, even 150 years to see how it looked then?

You can.

It’s called Old SF, an ambitious project that marries thousands of photographs from the San Francisco Public Library archive with Google Maps.

Click near the site of today’s Marriott Marquis hotel and check out the neighborhood in the aftermath of the 1906 earthquake. Then see what a difference 31 years made: The same street is crowded with traffic — cars bumper to bumper and not a parking space in sight.

Head a block southwest to Fifth and Mission and see the Old Mint before it was old. On its first day of business a line of people waiting for cash snakes from the top of the steps to the sidewalk toward Mission Street.

And across town along the Great Highway a group of smiling, waving kids packs into the “Rocket Ride” at Playland at the Beach.

That was in 1935. By 1972 the mood is somber as Playland comes tumbling down forever. Fifty-four other photos chronicle the decades of fun that Playland brought to visitors.

The project is the work of Dan Vanderkam, a software engineer, and Raven Keller, a designer. Vanderkam says the effort began

when he went to the San Francisco Public Library looking for a photo of his cross street. He found the picture, but the location was mislabeled, sparking the inspiration to put archived images on a map.

By “geocoding” the pictures with latitudes and longitudes and placing the results on a Google map, Old SF created a way to visit unfamiliar scenes in familiar places, to create customized historical walking tours and to virtually see the past — all from the convenience of the desktop.

Old SF isn’t the only way to peer into San Francisco’s history. The website “OpenSFHistory” likewise collects, organizes and displays scanned images. The pictures are searchable as well as organized by neighborhood, located on maps, and grouped in galleries.

OpenSFHistory was developed by the Western Neighborhoods Project, The project says the cornerstone of OpenSFHistory, about 100,000 negatives and prints, was provided by “a collector, who prefers to remain anonymous to the greater public.”