The United States declared war on Germany on April 6, 1917.  In May of that year, a new Aviation General Supply Depot was built close to Grant Street where  John Brinser had leased ground to grow cucumbers for the H. J. Heinz Pickle Company.  The Federal government also purchased an additional 40 acres of from the Stoner farmlands.

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The supply depot became a hub for air power, logistics, and storage.  Large warehouses were built.  Aircraft repair became a major activity.  Some of them stored completely assembled wings for various types of army aircraft and engines of all kinds.  A runway was built and the first flight was in 1918.  In 1919, the depot started hiring civilians to work in the warehouses and build parts.  

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In 1923, the depot changed its name to "Olmsted Field" in honor of Lt. Robert S. Olmsted who died in an air balloon crash caused by lightning. 

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By 1925, Olmsted Air Force Base controlled maintenence and equipment.  

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By 1931, the depot housed a large supply of Army aeronautical equipment and was able to turn out overhauled airplanes and engines at a rate of one per day.

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By 1939, Adolf Hitler was rising to power -- with another world war imminent and the demand to supply a full-fledged air force Olmsted was needed more than ever.

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After the bombing of Pearl Harbor on December 7, 1941, the United States entered WWII and more civilians were hired.  At the peak, Olmsted employed more than 16,000 men and women, along with 500 disabled persons.  Even the high schools tested students for typing duties. Young men became maintenance assistants.  More room was needed for storage and the government used the Farm Show Complex for training and buildings previously owned by the Old Pullman Standard Car Manufacturing Company were also taken over. Fifteen military detachments and squadrons were organized at Olmsted.  One of its most important duties was to turn out "compacs", which were a 30 day supply of parts and equipment, which weighed about 55,000 lbs each!  Olmsted was the only facility of its kind on the eastern seaboard.  It became a micro-system of life for those who lived on base with houses, tennis courts, a swimming pool, a putting green, mess halls,and various businesses including watch/clock repair.

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In 1948, Olmsted took part in the Berlin Airlift which sent 3,000 tons of food and coal each day from airbases in West Germany to Berlin's Tempelhof Airfield.

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In June of 1950, the United States entered the Korean Conflict and Olmsted set up an overhaul line for jet engines turbo-jet engines, and the jet bombers that were used at that time.

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Olmsted had over 1 million square feet of warehouse space and they continued to store supplies and parts.

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In July of 1967, the government deeded Olmsted over to the state, after selling off 177.5 acres to Penn State University for $1 in 1966, and it was officially closed in 1969.  The air field morphed into the Olmsted State Airport and later the Harrisburg International Airport.