Chirnside Park has a number of levels of significance:

- For its historic values as one of the earliest pastoral holdings of the area, including the very early (1850s) and architecturally significant homestead building. (RNE criteria D.2, E.1)

- For its historic significance as a rare example of a form of subdivision and social planning introduced from America in the 1960s. (RNE criterion F.1)

- For its association with a series of families notable both in the district and wider society, including the original settler William Fletcher, the Hon William Nicholson (1860-1884); William Jamieson, a Melbourne broker (1910-1916) and George Chirnside, grazier (1921-1940). For its historic association with the Chirnside family and its occupation and building works by George Chirnside. (RNE criterion H.1)

The current fabric of the former Mooroolbark Park Estate expresses three distinct stages of development.

The 1960s subdivision into the Chirnside Park Estate and Country Club, with its curvilinear residential subdivision surrounding an 18 hole golf course and country club based on the original holding is the current character of the place. The original stone gabled attic homestead is still clearly expressed within the fabric of the much expanded country club building and the original parterre area and large oak trees to its south still survive. There is also evidence of the occupation of the site in the Interwar period by George Chirnside, when major alterations and additions to the homestead were carried out along with formal landscaping and the construction of notable outbuildings. Of these changes only the U-shaped west service wing remains. These losses occurred prior to the Chirnside Park subdivision. The east and west gables were added to the original homestead and its present 'French Provincial' character, mainly expressed in dormers in the main roof, was established. The development of the site is generally as follows.

1) The original homestead, Mooroolbark Park.

The stone attic structure with the quadruple chimneys at either end is still clearly expressed at the centre of the built form of the country club complex. At closer quarters its origins are very clear and it is in many respects intact, although now enclosed on three sides by additions. In particular, the massive stone external walls with the splayed cased reveals to window and door openings are very evident. The upper attic floor and stair well are well preserved in full detail of door, casement window and stair joinery and plaster cornices. On the ground floor, the original floor plan is intact, although connections to additions have resulted in large wall openings in some places. Most of these are from the Chirnside period, a few later. On the ground floor, one (1880s) Victorian ceiling rose remains in the current manager's office and the cornices and window openings of the two north facing parlours are intact. Only the window sashes are new. The quality of the remnant early fabric is exceptional.

The gable (former kitchen?) wing projecting south from the south east corner of the two storey building probably also dates from this period.

There is no evidence of the encircling verandah, which was removed in the Chirnside modifications. The large oak tree probably dates from the early period. Further landscape analysis is desirable.

No photographs or other images of the early homestead have been found.

2) The Chirnside period (1921-40).

In the 1920s, George Chirnside transformed the former homestead into a modern country estate boasting among other things, formal landscaping, a two storey stable with a clock tower (destroyed by fire in 1990 but well recorded photographically) and a circular summer house with a domed shingle roof (See John Collins photograph, SLV, H97.250/2403). The modifications and additions by George Chirnside were substantial, but the name 'Mooroolbark Park' was retained. The character of the early complex was transformed into an Interwar bungalow mansion by the introduction of a number of additions, mostly (based on photos) of lightweight construction. They were;

- At the south side, a central two storey cross gable over what was probably the entry with attached flat roofed verandah and window hoods and a contiguous flat roofed sunroom(?) at the west.

- The sunroom continued from the west side to the full north elevation where the lightweight construction is apparent in the boarded undercroft and the framed fenestration above a paneled timber dado. This addition was surmounted by a full width second level of similar construction with an almost flat roof intersecting the original gable close to the ridge.

- The stylistic presentation of the building was made consistent by the introduction of wide eaves and vertically framed gable ends and the simplification of exposed chimneys to match the tapered chimneys of the new construction.

- To the east against the length of the projecting kitchen wing was added a service wing in the form of a U with a east facing courtyard with perimeter verandahs. The fretted verandah end infill valances are extant. The north elevation was also extended with a flat roofed structure, with similar fenestration to the service wing, serving as an elevated deck and carrying a steel tank stand.

- Internally the various openings between spaces on the ground floor probably date from this period.

- The large oak tree to the north was retained as a focal feature in a formal parterre landscape layout that included a lawn surrounded by cypress (?) hedges.

- The circular 'summer house' with a shingled domed roof surmounted with a finial, was located to the west of the house outside the parterre and roughly in line with the north elevation of the house. The stables and other outbuildings were located further west (based on the assumption that a photograph of the house and summer house was taken from the clock tower). There is no remaining physical evidence of any of these structures.

3) Intermediate period post war to the 1960s.

This would appear to be the period in which the Chirnside additions (except the service wing) were removed and the 'French provincial' character was introduced. The major changes, apart from stripping the Interwar character, including the wide eaves and gable ends were the introduction of lower parallel gables at the east and west, the latter in place of the flat roofed element carrying the tank stand. The other notable change is the introduction of three dormers to each side of the original attic. The U shaped service wing was retained (The courtyard is now filled in with a flat roof). The fabric at this stage is now defined by the structures roofed in slate. Records of this work were lost in the 1966 Shire of Lilydale fire.

4) 'Chirnside Park', the subdivision.

The 1960s subdivision of 'Mooroolbark Park' into a curvilinear residential development surrounding a golf course and 'country clubhouse' derives from American practice and is supposedly based on developments in California, Florida and Texas (The Wilmore and Randell brochure quotes a dozen American examples). Further research into the nature of subdivision practice and experimentation in the post war period is necessary to properly place this site, but it was an early example of this form of development in Victoria and an example where the American influence is fully expressed. Clifton Springs on the Bellarine Peninsula, also by Wilmore and Randell, is the only other known extant example. (The brochure also names the Pymble (Golf) Club, near Sydney (Cowan Road, St Ives), with pictures. This club goes back to the 1930s, so it is unclear if it was created as part of a subdivision or whether by occurring in a suburban context, it was merely good advertising material.)

The adoption of the name 'Chirnside Park' appears to derive from the status attached to the Chirnside family and their mansion, 'Werribee Park' as much as from the occupation of Moooroolbark Park by the son, George.

Physical Conditions: Good

Integrity: Evidence of stages