The article attempts at tracking down the processes in the political environment of Florida at the end of 1840s and 1850s which led to Florida's departure from the United States of America. Chronologically, the article covers the period between 1848, marked by the conclusion of the Mexican-American war and discussion of territorial expansion matters, and 1861, when the secession took place. This research aims to provide a stage-by-stage description of the secessionist movement development within Florida and determine the main causes of its departure in the early 1861. Such main causes are identified as a split in the Democratic party at the national level which took place at the 1860 party Convention, and considerable radicalization of Florida political elite supported by the governor's office and a significant number of mass media sources. And last but not the least role was played by skillful manipulation of public opinion existing in Florida in the 1850s. Further, this article studies the opposition of dem