A drop of water takes about 90 days to travel the length of the Mississippi River, from Lake Itasca in Minnesota to the Gulf of Mexico.
The Mississippi is approximately 2,340 miles long when measured from its traditional headwaters at Lake Itasca. Its water does not move at one constant speed: the upper river is relatively slow, while the current generally becomes faster and larger downstream as tributaries add water. Lakes, bends, wetlands, dams, and changing water levels also affect the journey.
The 90-day figure describes typical retention time for water moving through the river system, not a guaranteed stopwatch result for every individual molecule or droplet. A floating object could take longer because it may become trapped in eddies, backwaters, or vegetation. The Mississippi eventually empties into the Gulf of Mexico near New Orleans, carrying sediment and water from a vast watershed across the central United States.