Click on the 'Louisiana Census Maps' link for parish boundaries in the census year.
Select 'Parish Formation Maps' for a broad history of parish formation (some discrepancies noted).
-> You can also watch the parish lines change before your eyes [a little too fast for mine].

Note the brief intro to Census Schedules... especially the "Louisiana Indian" schedules ...

"...As early as 1860 the federal government began attempts to identify Native Americans. In 1900 and 1910 it created a special Indian schedule. The first page was the same as the population census only it had “Indian Population” as its heading. The second page provided for such important information as: tribal affiliation, the tribe of each parent, the person's Indian blood quantum, and—if not full blooded —their precise racial mixture. These schedules will be found at the end of the ward or district in which the Native American resided. ... "