Methane is a potent greenhouse gas with ~9 years of lifetime, a global warming potential of 30 over 100 years, and radiative forcing of 0.650 Wm-2 since 1750. In the 26th Conference of Parties (COP26), the US signed the Global Methane Pledge, which aims that by 2030, the emissions must be reduced by 30% relative to the 2020 levels. Hence, monitoring and quantifying CH4 emissions has become critical towards national greenhouse gas mitigation. In addition, COVID-19 disrupted normal human activities worldwide. Evidence shows that COVID-19 restrictions resulted in a reduction in air pollutants concentrations, however, more research is needed to understand the direct and indirect impacts of COVID-19 on greenhouse gas emissions. Here we present a detailed quantification of methane emissions over the contiguous US. We assimilated NOAA CH4 ObsPack GLOBALVIEW+ observations between December 2017 and January 2021. We used the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to simulate atmospheric transport with meteorology from the 12-km NAM nested with Global Forecast System with 0.25 degrees resolution (GFS0.25). We then conducted inverse modeling analyses with different background estimates and prior emissions. Our posterior estimates indicate a reduction of 2020 anthropogenic CH4 emissions compared to the 2019 of -6.1%, and -4.6% in 2021. The reduction in emissions occurred mainly in the south US. This presentation will discuss these 2020 CH4 emission anomalies and their underlying causes.