Hallinan did not play professional baseball again until he joined the Westerns of Keokuk, Iowa in . He played every inning of their 13 games at shortstop and, when the Westerns folded, moved on to the New York Mutuals for the remainder of that season and all of 1876, when the Mutuals were a founding member of the National League. With two home runs, he was third in the NL in that category. With three in 1875 he had ranked fourth in the NA. The Clipper observed that he, "being remarkably fleet of foot, was often credited with home runs."