The Current Employment Statistics program at the U.S. Bureau of Labor Statistics implemented revised Metropolitan Statistical Area (MSA) definitions with the release of its monthly employment estimates, effective with the January 2005 release. MSA geographical boundaries are determined by the Office of Management and Budget (OMB) and updated as new population data and information regarding commuting patterns become available. The conversion of existing time series for MSAs that added or lost counties under the new definitions and the creation of historical time series for areas that did not exist under the previous set of MSA definitions required significant analysis to ensure the integrity of the reconstructed data. We discuss the methods used in the reconstruction process in detail in addition to limitations faced and techniques innovated to address them. The methods shown here form the basis of the reconstruction process to be used in future years to keep CES state and area time series current on a near real-time basis with future MSA revisions issued by OMB.