Which archaeological discoveries revealed the Indus civilization in the 1920s?

The Indus civilization was first identified through major archaeological excavations initiated in the 1920s by the Archaeological Survey of India, under the direction of Sir John Hubert Marshall.12

These discoveries revealed two primary urban centers:

• Harappa: Excavations began at this site in the Punjab region in 1921. Archaeologists uncovered a large city featuring a fortified citadel on a raised platform, a grid-plan layout for workers' quarters, and significant infrastructure including granaries, circular grain-pounding platforms, and furnaces for metallurgy.312
• Mohenjo-daro: Identified in 1922 near the Indus River in the Sindh region, this site provided further evidence of the civilization's scale and sophistication. It shared a similar administrative layout to Harappa, featuring a citadel and monumental architecture such as the Great Bath.314

These findings pushed back the known history of the region to approximately 2500 BCE, revealing a highly organized society with standardized weights, measures, and urban planning.14