The reason for two towers is the fact that the waters of the Missouri and Mississippi are not sufficiently commingled at the Chain of Rocks. Tower #1 draws from Missouri River water, which flows closer to the shore, while #2 draws clearer water from the Mississippi, further out in the river.

By 1913, when construction of tower #2 began, the intake capacity of the older tower had become inadequate to meet the water needs of the City.