The purpose of this study was to compare average annual rates of mercury wet deposition and annual average ambient air concentrations of speciated mercury to changes in power plant mercury emissions. The wet deposition and atmospheric measurements were made at the Piney Creek Reservoir atmospheric monitoring station in western Maryland (MD 08). For total mercury deposition, the annual volume weighted total mercury concentrations decreased from 13 ng L^-1 in 1996 to 5 ng L^-1 in the early 2000s, but increased to 9 ng L^-1 in 2012. From 2005 to 2011, there were no reductions in the average annual ambient air concentrations of GEM. However, the average annual GOM concentrations decreased from 22 pg m^-3 in 2008 to 9 pg m^-3 in 2012. Similarly, the average annual PBM­_2.5 concentrations decreased from 7 pg m^-3 in 2007 to 4 pg m^-3 in 2012. These downward trends were consistent with reductions in mercury emissions from power plants. For example, power plant mercury emissions in Pennsylvania decreased from 2.75 tons yr^-1 in 2007 to 1.95 tons yr^-1 in 2011.