The large limestone façade of the Nassau County Court House dominates the stretch of Old Country Road between County Seat Drive and Washington Ave. Constructed in 1940, the three-story Court House houses 17 judges and county courtrooms on the first and third floors. The Court House also is home to the offices of the Nassau County District Attorney and Clerk of the Court, which occupy the second floor of the Northern and Southern halves of the building, respectively. The Northern half of the third floor is also home to the Surrogate's Court. In the center of the Court House lies the Great Hall, a skylight enclosed space with various displays including copies of both the U.S. and New York State Constitutions, a tribute to fallen officers of the September 11 attacks, and a large glass-enclosed map of Long Island and the surrounding area.
The home of New York State's 10th Judicial District Supreme Court is located just to the south of the Nassau County Courthouse. First opened in 1962, the building is where all Nassau County residents who are summoned for jury duty must report before being assigned to trials. The Supreme Court building is also home to the Nassau law library, located on the second floor.