The first U.S.-built ISS module delivered by a Space Shuttle was Unity.
Also called Node 1, Unity was carried aboard Space Shuttle Endeavour during STS-88 in December 1998. Astronauts attached it to Zarya, the Russian-built control module already orbiting Earth, creating the starting point for the International Space Station’s on-orbit assembly.
Unity is a connecting hub rather than a major laboratory or living module. Its six berthing ports allowed later station elements to be attached, including the U.S. laboratory Destiny, the Quest airlock, and the Harmony node. It also routed power, data, fluids, and other services through the growing station.
The wording “first U.S.-built” matters. Zarya was the first ISS module launched, but it was built in Russia, despite being funded by the United States. Harmony, Quest, and Destiny were all delivered later. Unity’s STS-88 delivery therefore marks both the first U.S. station element in orbit and the first shuttle mission dedicated to ISS assembly.