The Federal Building and Post Office jointly located in one building on the corner of Locust and Clay streets in Chillicothe, Missouri, was constructed in a grand rectangular size, with three-floor levels in the Beaux-Arts architectural style, which is a French Neoclassic decorative structure with accents in Rennaisance and Baroque. This style coincides with the European Classical movement in American architecture in the nineteenth century.
The City of Chillicothe sent a proposal to the Secretary of the Treasury in Washington D. C. for funds to build a federal building for the post office in 1908. Congress had formulated a plan to donate funds to several cities and towns nationwide, including Missouri, to create a federal public building appropriation bill. Two years later, a contract was signed by a Kansas City assistant United States Marshal with real estate agents from Chillicothe by selling the corner lots on Locust and Clay streets to the government as the new location for the post office building. Various States are planning to receive $11,000,000 to construct federal buildings, and Chillicothe was awarded $65,000 in 1910. On May 4, 1912, Congress passed the Post Office appropriation bill authorizing $275,000,000 along with aid to pave roads. Chillicothe is awarded a total of $130,000 to expand the size of its building by placing the Federal court within its walls. The city is required to serve two terms of the Federal court.
By 1914, a government official consented to the drafting plans for the Federal Building in Chillicothe. The three-story building is to be fireproof, have a tile roof, marble tile floor for the lobby, and a metal screen for the post office. Within the next year, proposals were sent to the Treasury Department in Washington D.C. to secure architects, superintendents, and contractors. In September, concrete was applied for the foundation of the Federal building. In early April 1916, the construction of the Federal building was completed. By October, the building passed the final inspection but the last-minute installations of fixtures and furniture in the post office mailing room stalled the opening. A formal opening of the post office was held on March 24, 1917. Due to the atmosphere of the First World War, the Federal court did not function in the building. Instead, the United States Navy and Army recruitment offices, civil service examinations, the Red Cross, and the Daughters of the American Revolution (D. A. R.) relief aid organizations occupied the spaces.
In the 1920s, the Federal Farm Loan office and the Census office opens in the Federal building. Improvements were made to the windows, post office screens, painting, and repairs to many departments. In November 1926, the courtroom and Federal office finally opened in the building, which the room had been furnished since 1916. In 1933, the outside of the building had been repainted since its construction but with the same colors of yellowish brown intact. The Agricultural Conservation office was on the third floor for county farmers to pick up their checks in the farm program. In the 1940s, the Federal Bureau of Investigation and the Extension Club offices were located at this location. The Extension Club office was a meeting place for lumber, hardware, and feed dealers in Livingston County.
In 1955 and 1958, the Federal building had undergone more interior improvements. The post office was repainted and new fluorescent lighting was installed. All three floors, including the basement, had received air conditioning for the first time. A new location for the post office was selected on Washington street in February 1960. The post office space on the first floor will provide for other offices and agencies. The agencies operating in the Federal building are the post office, Social Security Administration, the University Extension Center, the Internal Revenue Service, American Cross, Soil Conservation Service, the Selective Service, and the State Highway Department. By 1964, the post office property in the building was listed officially as unused property by the United States General Services Administration, as the new post office building was undergoing construction. Public agencies were available to use the space until 1965. By 1965, the Federal building became the main site for the Livingston County Memorial Library, while other agencies still occupied their office space. The County Library currently provides services to researchers and patrons today.