The Cairo Custom House is one of the historical buildings found in the County of Alexander. It was constructed in 1972 for the purpose of collecting tariffs from the heavy import trade passing Cairo through the Illinois and Ohio rivers. Buildings used to be occupied by a post office, a courtroom, and other government agencies. The building?s site was chosen by Stephen A. Douglas in 1859. However, the construction did not immediately start. It was only in 1866, after the Civil War, which the building process began. John A. Logan came back to Congress. He was able to lobby $50,000 for its construction. From that time on, $50,000 was allotted to it every year until its construction was completed on June 16, 1872.

The building was designed by Alfred B. Mullet, an architect who was known for being extravagant with his buildings. His other building designs are the US Treasury Department, the St. Louis Post, and a certain addition the White House.

The Cairo Custom House features black slate and white marble square tiles that collectively resembles a checkerboard. Its fireplaces used Italian marble and slate from Vermont was used for its roofing. Other materials used for the house are walnut wood and cast iron, which represents the extravagance of its designer.