Delaware Route 100 (DE 100) is a state highway in New Castle County, Delaware. The route runs from DE 4 near Elsmere to the Pennsylvania border near Montchanin, where it continues into Pennsylvania as State Route 3100 (SR 3100, Chadds Ford Road). The road runs through suburban areas of northern New Castle County. It intersects with DE 2 in Elsmere and DE 34 north of Elsmere before forming separate concurrencies with DE 48 and DE 141 from west of Wilmington north to Greenville. In Greenville, there is an interchange with DE 52. North of Greenville, DE 100 continues by itself to the Pennsylvania border, intersecting DE 92 in Montchanin. DE 100 was first designated in the 1930s to run from DE 52 to the Pennsylvania border, where it originally connected to Pennsylvania Route 100 (PA 100). By the 1970s, it was extended south to DE 4. The route was realigned to follow parts of DE 48 and DE 141 by 1990.