It was first called the Indus Valley Civilization. But later it was named as the Indus Civilization. 

The earliest excavations in the Indus Valley were done at Harappa in the West Punjab and Mohenjodaro in Sindh (both now in Pakistan)

Origin and Evolution

Gradual development with four important stages or phases of evolution- pre, early, mature and late Harappan phases.

Pre-Harappan stage :

• Located in eastern Balochistan. The excavations at Mehrgarh 150 miles to the northwest of Mohenjodaro reveal the existence of pre Harappan culture 
• The nomadic people began to lead a settled agricultural life

Early Harappan stage :

• People lived in large villages in the plains
• There was a gradual growth of towns in the Indus Valley
• Also, the transition from rural to urban life took place during this period 
• The sites of Amri and Kot Diji remain the evidence for early Harappan stage

Mature Harappan stage :

• Great cities emerged. The excavations at Kalibangan with its elaborate town planning and urban features prove this phase of evolution

Late Harappan stage:

• Decline of the Indus culture started
• The excavations at Lothal reveal this stage of evolution 
• Lothal remained an emporium of trade between the Harappan civilization and the remaining part of India as well as Mesopotamia 

Date of Harappan culture:

• The advent of the radiocarbon method paves way for fixing almost accurate dates
• D.P. Agarwal concluded the total span of this culture should be between 2300 and 1750 BCE

Important sites

• Kot Diji in Sindh
• Kalibangan in Rajasthan
• Rupar in Punjab
• Banawali in Haryana
• Lothal, Surkotada, Dholavira in Gujarat