In 1830, the census listed 15 heads of households, and a total of 733 persons, mostly slaves. In January 1835, the county seat was moved to New Smyrna. However, the Second Seminole War had largely depopulated Mosquito County of white settlers by the end of that year. In 1838, there was so little activity in the county that the St. Johns County Clerk was designated to keep the records of the county. However, by 1840, although the census listed no white inhabitants other than the military personnel based at Fort Pierce and New Smyrna, the county had its own officials.