Longest and Largest Rivers in the Americas

Longest: Missouri–Mississippi River system — ~3,734 miles (6,010 km) from Brower's Spring, MT to Gulf of Mexico.

Largest by discharge volume: Amazon River — ~209,000 m³/s (7.4 million ft³/s) at mouth, draining the world's largest rainforest basin.

Note: The Amazon's main stem lies mostly in South America (Brazil, Peru, Colombia); the Mississippi–Missouri is entirely in North America (USA).