When the Harrisburg the central business district (CBD) for 1960, delimited according to the regular CBI system, was compared with that resulting from use of Paul F. Mattingly's modified system, it was found that the latter was ten blocks larger in area. Mattingly's study dealt with changes through time and thus to some degree was historical, but the time period involved was limited and concern was chiefly with the changing CBD boundary. David Ward points out that much of the internal complexity of many CBDs of today is rooted in changes associated with the Industrial Revolution. The warehouse district, which was by far the largest segment of the CBD in 1875, continued to expand southward during the last decades of the nineteenth century. North of State Street, the market halls had provided cramped accommodations for the fresh food and provision trade. Traffic congestion within Boston's CBD was intensified by the wide separation of railroad and waterfront terminal facilities.