Wallacia was originally called Riverview, but was known locally as Wallace after the cattle farmer Robert Wallace who rented 2000 acres from Sir Charles Nicholson. Wallace's house became the areas unofficial post office in 1885 and by 1897 a school had been built in the area and was called Wallace School.
The post office was made Official in 1905 and GPO renamed the area Boondah, due to Wallace was already in use within NSW. In 1906 due to local objections the name Wallacia was approved to maintain the links to the Wallace family. Another well known local, John Blaxland, also farmed in the area, building a weir at "Grove Farm" for a flour Mill and brewery but the flour mill failed when rust got into the wheat crop.
Grove Farm was sold to George Cox of Windbourne, in Mulgo and later to William Baines, who's name was given to a hill on Silverdale Road. Baines also marked the 1873 flood, the highest recorded for the Nepean River, with a Sandstone and brass plaque near the barn at Grove Farm, which still bears the water marks.
