volusia county is a county in the east-central part of the u.s. state of florida. it is bordered by st. johns river to the west and the south, with the atlantic ocean to the east. the county was founded on december 29, 1854. at the 2010 united states census, 494,593 people lived there. it is the sole county of the deltona–daytona beach–ormond beach, fl metropolitan statistical area. the county seat is deland, and the largest municipality is deltona.