Background concentrations, emission rates, and trends in emission rates for five trace gases are inferred for the northeastern United States from continuous atmospheric observations at Harvard Forest in central New England for 1996--1998. Mixing ratios of gases regulated by the Montreal Protocol (CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CCl2F-CClF2), CH3CCl3, and halon-1211 (CBrClF2)) are referenced to CO and PCE (perchloroethylene, tetrachloroethene, C2Cl4) to determine their urban/industrial source strengths and to test existing estimates of U.S. emissions. Despite the full imposition by 1996 of the Montreal Protocol ban on production by developed countries, our data show that significant releases to the atmosphere continue and that only emissions of CFC-12 and CH3CCl3 declined in the region during this period. A broader historical and geographical study of emissions reveals that from 1986 to 1996 the international treaty has reduced U.S. emissions of CFC-11, CFC-12, CFC-113, and CH3CCl3 by 87%, 70%, 93%, and 87%, respectively, but current trends suggest persistent emissions for many years following.