The Indus Valley Civilization was a Bronze Age civilization that flourished along the Indus River in what is now Pakistan and northwestern India between 2600-1900 BCE. Major cities included Harappa and Mohenjo-Daro, which had populations of around 40,000 people and were laid out in an organized grid pattern with advanced water and drainage systems. The civilization engaged in extensive trade of materials and surplus agricultural goods. While the writing system remains undeciphered, artifacts provide evidence of a complex society and political system that governed through trade and religion rather than military force.