McLean's Mansion, first known as Holly Lea, was built for Allan McLean (1822-1907). McLean had arrived in New Zealand from the goldfields of Australia and took up a number of large sheep stations in partnership with his brothers John and Robertson. Robertson soon left the partnership and in 1880 John and Allan dissolved their agreement, with Allan taking Waikakahi station, and John Lagmhor and Waitaki. The history of Holly Lea is closely associated with government policy on these and other large estates.

Since the 1870s there had been calls for closer settlement of the land and for the government to 'bust up the big estates'. In 1882, 32 percent of runs that consisted of 10,000 acres or more was held by less than one percent of the owners and large holdings were particularly common in Canterbury. In 1891 the Liberal party came into power on the back of a campaign to put more people on the land, using compulsory purchase of land from the large estates when necessary. Most of the more than two million acres made available for closer settlement occurred through the voluntary sale of land by the large runholders. McLean was initially a reluctant vendor and was only persuaded to sell Waikakahi after some pressure from the then Minister of Lands, John McKenzie. In the event, Waikakahi became the first property sold to the Crown under the Public Lands Act.

Holly Lea, the house McLean built from the proceeds of the sale of Waikakahi, was built from kauri and was the largest timber house in Christchurch, containing 53 rooms. The house was designed by Robert William England, whose firm, the England Brothers, became noted locally for their domestic work. The design for the house was derived from Sir Joseph Paxton's Jacobean-style Mentmore Towers in Buckinghamshire. The Jacobean style often featured an eclectic mixture of Flemish, French and Italianate ornamentation, evident in the diversity of styles used in the design of Holly Lea. The notable features of the house include the two, three-storeyed towers on either side of the front entrance, and the central hall, which is lit by a massive glass skylight and has an arcaded gallery running around it.

In his will McLean established a trust that was to provide a 'home for women of education and refinement in reduced or straitened circumstances'. The McLean Institute provided such homes for a number of years in various houses around the city, and eventually in McLean's Mansion itself, after McLean's former housekeeper left Christchurch.

In 1955 the Trust decided to sell Holly Lea, due to both the financial difficulties of the Institute and to a shift in ideas about appropriate accommodation for the elderly. Smaller and warmer rooms, rather than the spacious grand rooms of Holly Lea were now deemed to be more appropriate. The beneficiaries living at Holly Lea at this time were moved into accommodation at 'Quamby', the Institute's second home in Fendalton, which is still, as of 2002, being run by the McLean Institute as a home. It is now known as 'Holly Lea'.

The Trust sold the house to the government for use as a hostel for dental nurse trainees. A lack of staff was a major problem for the New Zealand School Dental Service during the early 1950s. The service embarked on a recruitment drive and in 1955 opened a third training school in Christchurch. The trainees were housed in Holly Lea until 1977; the house subsequently stood empty for ten years while the government tried to find a long-term use for the building. In 1987 it was bought by the Christchurch Academy, a vocational training organisation.

Holly Lea, now known as McLean's Mansion, is significant as one of the largest timber houses in New Zealand and is a well known and publicly appreciated part of Christchurch's architectural history. Its Jacobean features, built in local materials, are particularly interesting. Historically, its link to the break-up of the great estates is interesting, as is the house's link to the McLean Institute, which demonstrates the past importance played by private philanthropists in the provision of the community's welfare needs. The house also played a role in the history of the New Zealand School Dental Service.