1818 Market Street is a 40-story skyscraper in downtown Philadelphia, Pennsylvania. The building, designed by the firm Ewing Cole Cherry Brott (now EwingCole), was the tallest building erected in Philadelphia between the completion of City Hall in 1901 and the completion of One Liberty Place in 1987, during the period of the "gentlemen's agreement", the observation of an unofficial height restriction of the top of the hat of the statue of William Penn atop City Hall (548 feet/167 meters) that stood for 86 years.
The building contains over 981,000 square feet (91,100 m2) of office space over 37 floors with six levels of parking. Its major tenants include Merrill Lynch, Mitchell & Titus, Northwestern Mutual, Booz Allen Hamilton, ABN Amro, eResearch Technology, Swiss Re, STV Incorporated, and the offices of Philadelphia Magazine. The building, currently the tallest reinforced-concrete structure in the city, underwent major renovations in 2003, more than a decade after its facade was treated resulting in its signature white color.