Historian Kenneth T. Jackson and others theorized that Newark, with a poor center surrounded by middle-class outlying areas, only did well when it was able to annex middle-class suburbs. When municipal annexation broke down, urban problems were exacerbated as the middle-class ring became divorced from the poor center. In 1900, Newark's mayor had confidently speculated, "East Orange, Vailsburg, Harrison, Kearny, and Belleville would be desirable acquisitions. By an exercise of discretion we can enlarge the city from decade to decade without unnecessarily taxing the property within our limits, which has already paid the cost of public improvements." Only Vailsburg would ever be added.