In June, 1840, Simson entered a partnership with William Hampden Dutton, an agricultural scientist and pastoralist and James Monckton Darlot, an overlander and explorer.

He was at various times assisted in running it by his two brothers, John (1798/9-1848) and Hector Norman (1819-1880), who did not, as has for many years been claimed in many newspaper articles, book and pamphlets written on the subject, participate in founding the station.

The original partners took Fourteen Mile Creek station and at the same time Simson alone took over Cairn Curran from Dutton's associate, the Melbourne businessman Frederick Manton.

The lease of Cairn Curran was taken over by Frederick Langdon and George Ward Cole In November 1841, and some time after it was unofficially occupied by Edmund Bryant when he relocated to Port Phillip from Van Diemen's Land with his family.

With an excellent stock capacity and profitable wool production, Charlotte Plains was one of the Port Phillip colony's most important sheep station in the 1840s, but it went into decline after Simson's death in 1851 and in the 1860s and 1870s his two surviving sons exploited it until they had sold off its last lands by 1884.

The well-known engineer and World War I general, Sir John Monash, designed and built a new bridge of reinforced concrete beam and slab construction and it still stands today.