Vestby is a municipality in the county of Akershus, Norway. Main villages are Vestby, Pepperstad Skog, Hølen, Hvitsten , Garder, and Son . Son was, from the Renaissance until the 1700s, an important harbour. On some Dutch maps from that time, Oslofjord is called Zoon Water. Archeological studies in Hølen has confirmed that the area has been populated since about 2400 BC. The municipality and town of Vestby is both named after the most important farm in the area.