Invented by Henry Gantt, a teacher, mechanical engineer, and one of the first productivity specialists, Gantt charts were originally used to track employee productivity.  The first Gantt charts were a very humble method for tracking the progress of factory workers compared to a standard level of performance.   Current Gantt charts list the steps in a project and illustrate when each step is expected to begin and end.  Early uses  of the Gantt chart for project management were the Hoover Dam Project (1931) and the Eisenhower highway network (1956).

An early Gantt chart

A modern version of the Gantt chart

Milestones Professional Schedule