PlaceLayers › Then and now overlay
Then and now, on one map
Fade a historical map into today’s. 268 georeferenced USGS quadrangles covering 127 American places, 1880s to 1990s. Street lines move, blocks get cut in half by a highway, a rail yard becomes a parking lot. The slider is the point: keep it moving.
70%
Today’s base map
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What the overlay is and is not.
Historical quadrangles are placed on the corner coordinates printed on the sheet. Nineteenth and early
twentieth century surveying, paper shrinkage and scanning all introduce positional error, so treat the
overlay as indicative at street scale and never as a parcel boundary. Nothing here describes the condition
of any property. How we handle positional uncertainty.
Why this view answers a different question
Street pattern changes
Alleys, wharves and rail spurs disappear from modern maps but they tell you where industry sat. Fading between the two shows you which of today’s lots are made of yesterday’s yards.
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A topographic map shows shape and use at the landscape scale. For building-by-building detail on a Baltimore block, go to the Sanborn sheets.