The first known house here was built in the sixteenth century for Sir Richard Morrison, who had been granted the manor of Cassiobury by Henry VIII in 1545. In the late seventeenth century, when the manor was owned by the Capel family, the house was partially rebuilt. In 1661, Arthur Capel was created Earl of Essex by Charles II when the king returned to England. The House was rebuilt in the early 1800s for the Fifth Earl of Essex, when it was extended and “gothicised” by James Wyatt, when battlements and other features were added. It was this house which was demolished in 1927.
The Capels had already had to sell land to developers from the 1890s and in 1909 Watford Urban District Council bought 49 acres of the park to create a ‘people’s park”. Additional land was bought by the Council between 1913 and 1930 to create to the park as it is now. It has already been awarded a “Green Flag” and there are plans to improve the facilities and interpretation with a grant from the Heritage Lottery Fund.