CENTURY 21 Alliance was formed through the strategic merger of several of the most successful CENTURY 21 firms in Southeastern Pennsylvania. Selling more homes than any other CENTURY 21 Company in Pennsylvania and currently ranking Top 3 in homes sold in the entire United States for the CENTURY 21 ? System , CENTURY 21 Alliance has the experience that today's consumers need in the buying and selling of real estate. Currently there are 15 offices and over 600 sales associates of CENTURY 21 Alliance serving Southeastern Pennsylvania, providing a full range of services for Buyers, Sellers, Builders and Investors.