Brevard County , the oldest one of this counties, was established in 1844, while Osceola County was created in 1887. Indian River County is the newest one, established in 1925.
In terms of demographics, Indian River County had 138,028 people as of 2010, while Osceola County had 268,685 people. Brevard County, on the other hand, had 543,376 people in the same year, making it the 10th most populous county in Florida.
Finally, in regards to their extension, Brevard County is the largest county, with 1,557 sq mi (4,033 km2). Osceola County comes in second place with 1,506 sq mi (3,901 km2). Finally, Indian River County is the smallest one, with 617 sq mi (1,598 km2).
