On July 3, 1871 Brookings County was formally organized and named after him. The city of Brookings, South Dakota was also named for him, though he only ever visited the town twice. In 1871 Brookings helped organize the Dakota Southern Railroad, and spent the next ten years serving as an executive for the railroads that would eventually become part of Chicago, Milwaukee, St. Paul and Pacific Railroad. Brookings was among the first to ride a locomotive into Dakota Territory when the first Dakota Southern train entered the region on October 1, 1872.