The New Hampshire Commuters Income Tax treated income earned by residents and non-residents differently. New Hampshire residents were not taxed on income earned in-state or out-of-state, whereas non-residents were taxed on income earned within New Hampshire. Austin was a Maine resident who commuted to New Hampshire for his employment. Austin filed suit against New Hampshire in state court arguing that the tax violated the Privileges and Immunities Clause and Equal Protection Clause of the state and federal constitutions. The trial court transferred the matter to the Supreme Court of New Hampshire, which upheld the validity of the tax. The United States Supreme Court granted certiorari to review.