Ullin is a village in Pulaski County, Illinois, United States. The population was 466 at the 2020 census. Ullin was established as a site along the Illinois Central Railroad in the mid-1850s. Some sources suggest it was named for a Gaelic folk hero who frequently appears in the works of the poet Ossian. Other sources suggest it was named for its first postma…Ullin is a village in Pulaski County, Illinois, United States. The population was 466 at the 2020 census. Ullin was established as a site along the Illinois Central Railroad in the mid-1850s. Some sources suggest it was named for a Gaelic folk hero who frequently appears in the works of the poet Ossian. Other sources suggest it was named for its first postmaster, Samuel Ulen. A post office was established in 1856, and the village was platted the following year. Ullin incorporated in 1900.