What contemporary engineering feats resonated with the public imagination, framing the interpretation of Martian lines as massive construction?

Answer

Suez and Panama Canals

The context of major terrestrial engineering projects like the Suez and Panama Canals made it natural for observers to interpret straight lines on Mars as symbols of massive human-scale construction.

What contemporary engineering feats resonated with the public imagination, framing the interpretation of Martian lines as massive construction?
MarsastronomyvegetationCanalsLowell