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Age Detail for Infrastructure on Each Major River System

FIGURE D-1 Comparison of lock infrastructure construction year (indicated by colored markers) and rehabilitation year (indicated by label callout) for the Upper Mississippi, Illinois, Ohio (including Allegheny and Monongahela), and Columbia River systems.
SOURCE: U.S. Army Corps of Engineers Navigation Data Center: Lock Use, Performance, and Characteristics, http://www.navigationdatacenter.us/data/datalck.htm.