U.S. States: Louisiana: Saint Helena County
Indeed, a part of LA was in the Spanish West Florida Province until about 1810 when it revolted and overthrew the Spanish. This area was not a part of the Louisiana Purchase of 1807 because it was Spanish, whereas the area west of the Mississippi River was French dominion.
It was a 'republic' for a very short period before being recognized as a 'territory' of the United States. Later still, it was incorportated into that larger territory which became the state of Louisiana.
The 'Florida Parishes' are generally all those parishes (read counties) which lie east of the Mississippi River and north of Lakes Ponchartrain and Maurepas, and south of the 31st parallel, which is today's MS/LA state line on the 'toe' of LA.