Several annual mesoscale convective complex (MCC) climatologies have been compiled since Maddox strictly defined their criteria over two decades ago. These previous studies have largely been independent of each other and therefore have not established the extended spatial and temporal patterns associated with these large, quasi-circular, and, typically, severe convective systems. This deficiency is primarily due to the complexity of archiving enough satellite imagery to accurately record each MCC based on Maddox’s criteria. As a result, this study utilizes results from each of the MCC climatologies compiled between 1978 and 1999 in order to develop a more complete climatology of these storms. Within the 22-year period, MCC climatologies were compiled for a total of 15 years. These 15 years of MCC data are employed to establish estimated tracks for all MCCs documented and, thereafter, utilized to determine MCC populations and densities on a monthly, seasonal, annual, and multi-year basis. Subsequent to developing an extended climatology of MCCs, the study ascertains the spatial and temporal patterns of MCC rainfall and determines the precipitation contributions made by MCCs over the central and eastern United States. Results indicate that there is a large amount of yearly and even monthly variability in the location and frequency of MCC events that, in turn, has substantial impacts on the hydrological and severe weather climates of the central and eastern United States – specifically during the warm season.