Casey successfully ran for a seat in the United States House of Representatives for the newly created second district in the election of 1832.

During his time in Congress, Casey was able to help secure a land grant to finance the creation of the Illinois Central Railroad.

While serving in the Illinois House of Representatives, Casey had also voted in support of a proposed state constitutional convention in 1824.

[5] He died in Caseyville, Illinois at age 66, and was interred at Old Union Cemetery in Mount Vernon.

Caseyville, Illinois, was named after Zadok Casey due to his help to finance what eventually became the Ohio and Mississippi Railway (later operated by CSX Transportation) which ran through the center of town.