XML is integral to the US Federal Enterprise Architecture. Its use is actively encouraged by the Office of Management and Budget (OMB) and the E-Government Act of 2002. This paper provides a high-level view of a number of mature XML efforts in the US federal government, including efforts of the CIO Council, E-Government Initiatives, Dept. of Navy (DON), Environmental Protection Agency (EPA), General Services Administration (GSA), Dept. of Justice (DOJ), Small Business Administration (SBA) and others.