[2][3] The church contains a mechanical organ that was built in 1868 by J. W. Walker of London, with a manual compass of 56 notes, a hitch-down Swell pedal, with 159 pipes.

[4] Between 1809-c. 1904 early land grants were made in the valley to the notable Cox family and were noted for pastoral use, vineyards and orcharding.

They left behind four buildings - Glenmore, Fernhill, The Cottage and St. Thomas's Church - reflecting the early pioneering phase, their era of prosperity and their social and religious aspirations.

[5][2] This is a hillside site north of Mulgoa township in a semi-rural area sloping south and east, facing St. Thomas's Road, bordered with regrowth eucalypt seedlings.

The church has a picturesque graveyard of clustered headstones and notable classical sandstone monuments, predominantly of the pastoralist Cox family.

The location of the original rectory building has been established on the ridge south of the church (refer to A121/1 and the 1947 aerial photo where it was still standing).

[2][11] As at 12 May 2004, St. Thomas' is the only extant example of a reasonably intact, late 1830s Gothic Revival, rural Anglican parish church in New South Wales.

The picturesque graveyard of clustered headstones and notable classical sandstone monuments, predominantly of the Cox family, is on a sloping site alongside, bordered with eucalpyt saplings, and complements the church admirably.

It remains one of the most romantic rural church settings in New South Wales, and has significance both for its superb landscape value and its relative intactness.

[14][2] St Thomas' Anglican Church, Mulgoa was listed on the New South Wales State Heritage Register on 2 April 1999.