 One of his last major commissions was for the gothic, brownstone library (Rich Hall, 1866–68), now Patricelli '92 Theater, at Wesleyan University in Middletown, CT.

After the 1860s, Austin's style changed with the times, incorporating structures in the Second Empire and Stick styles.In 1868, he constructed two Second Empire houses on Prospect Street in New Haven for Oliver Winchester and David Russel Brown.The Winchester House has been demolished, but the Brown house remains, having been restored by Yale and renamed the Betts House.