Final answer:
The Chattahoochee River is the significant water source for American Indians, European settlers, and modern residents of Georgia's Piedmont. It has supported various activities and development in the area throughout history and continues to be a vital resource today.
Step-by-step explanation:
The water source significant to American Indians, European settlers, and millions of Georgians living in the Piedmont today is the Chattahoochee River. This river has played an essential role in the development of the region, serving as a source of fresh water, transportation, and facilitating agriculture, including the sophisticated irrigation techniques introduced for tidal rice cultivation by Africans in Georgia's Low Country.
Both the indigenous populations and the Europeans recognized the importance of the Chattahoochee River. Over time, it became a lifeline for those living in its vicinity, supporting a vast array of economic activities and community development. The river continues to be a crucial resource for drinking water, recreation, and economic activities in the Piedmont region of Georgia.