is a form of government in which the ruling power belongs to a just a few people. Oligarchy can also refer to the people who rule that type of government.
Oligarchies aren't new. Upton Sinclair's The Jungle, published in 1906, exposed abuse in Chicago's businesses and government that most certainly existed, for graft was a way of life. In all probability, The Jungle illustrates a world that was not too far removed from the reality of the day; however, the extreme examples of abuse in the novel are most likely the result of Sinclair's imagination.
And so Jurgis got a glimpse of the high-class criminal world of Chicago. The city, which was owned by an oligarchy of businessmen, being nominally ruled by the people, a huge army of graft was necessary for the purpose of effecting the transfer of power. Twice a year, in the spring and fall elections, millions of dollars were furnished by the businessmen and expended by this army; meetings were held and clever speakers were hired ... and tens of thousands of votes were bought for cash.