Progress report on the construction of the Navy Prototype Optical Interferometer at the Lowell Observatory

The Navy Prototype Optical Interferometer (NPOI) at the Lowell Observatory near Flagstaff, Arizona is a tri-baseline stellar interferometer with specific design characteristics for astrometry and imaging. All major construction has been completed. Installation of scientific instrumentation began in July 1993 with first light expected during the Spring 1994. Here we present a description of the location, physical plan, and construction of the interferometer.