The streetcar borough by the Yellow Breeches

New Cumberland grew up where the Yellow Breeches Creek meets the Susquehanna, and it grew up mostly in one push: the streetcar decades, roughly the 1900s through the 1930s, when the trolley lines made the West Shore commutable. The result is a borough of American Foursquares and frame colonials (porches, deep narrow lots, sidewalks) built before anyone poured a modern basement. Below those frame houses sit the era’s foundations: stone in the earlier blocks, first-generation block in the later ones, cellars dug low with utilities threaded through them for a century since.

Frame construction fools people here. Owners assume an old wood house is somehow a different radon case than a brick one, but the gas never sees the siding. It negotiates with the cellar, and New Cumberland’s cellars are period pieces. Original floor slabs poured thin and patched often; walls whose mortar joints have breathed for ninety years; and the borough’s riverside setting adding its own wrinkle, because homes near the creek and river carry generations of moisture management, sumps and drains and re-graded floors, that rearrange how air moves under the house.

The borough also climbs. Away from the flats, streets rise up the hillside toward Lower Allen, and the housing shifts younger: postwar capes, then split-levels stepped into the slope. Splits are their own radon animal: half-basement, half-slab-on-grade, two foundation systems sharing one footprint, sometimes needing suction on both.

All of it sits at the eastern edge of the same Cumberland County limestone that earns the county its Zone 1 rating from the EPA. The published local numbers, down to ZIP grain, are collected in radon levels in your area, worth a look before assuming anything about a specific block.