In the 1890 's and for some time thereafter , Hartford was known as the richest city in the United States , so wealthy that Mark Twain , who rented a pew but was not a member of the Asylum Hill Congregational Church , would tease his good friend , the Rev . Joseph Twichell by calling his church '' the Church of the Holy Speculators , '' according to Alfred Bigelow Paine who was Twain 's biographer .