Save Kilmorie, 21 Withrow Avenue - William Wilfred Campbell was a Person of National Historic Significance.

"William Lyon Mackenzie King and Friends". Front, left to right-Norman Duncan and William Wilfred Campbell.
 Back-W.L. Mackenzie King and Henry A. Burbidge. 

The homes and landscapes of many other Canadian National Historic Persons are preserved. For example:
Bliss Carman House - Confederation Poet- 83 Shore Street, Fredericton, New Brunswick.
Emily Carr House National Historic Site of Canada - 207 Government Street, Victoria British Columbia. Now an art gallery and an arts centre.
E. Pauline Johnson (Tekahionwake) - Chiefwood, Brantford, Ontario.

Chiefwood is now a National Historic Site. Pauline Johnson grew up in this house. The adjoining park encompasses 20 acres of land. (The article is from 1962.) 

The Marshall McLuhan House - 11342 64 Street NW, Edmonton, Alberta - to see a video of the restored property Google: "Renovations complete on Marshall McLuhan House"cbc.ca.
L.M. Montgomery's Cavendish National Historic Site, Cavendish, Prince Edward Island. - Lucy Maud Montgomery was the author of Anne of Green Gables.
(more)
Archibald Scott built the house and the Scott family donated land along Merivale Road to the nearby Experimental Farm.
 Fairfields Heritage House located at 3080 Richmond Road was donated to the City of Nepean (which later became the City of Ottawa) by Ruth Bell in the year 2000.The gift included 1.84 acres of land and many trees.

The Writer's Trust of Canada owns the domicile where Canadian writer Pierre Berton grew up in Dawson City,Yukon. The Canada Council for the Arts and fundraising dinners cover the cost of maintaining the historic site.
Contact The Canada Council

A photograph of my Dad and Pierre Berton at CJOH-television, 1500 Merivale Road, 1962.

 91 acres of open space a mile away were lost forever, when Experimental Farm land was sold to the Municipality of Ottawa in 1988.

I live about 15 minutes away from Fairfields House, 3080 Richmond Road. When the property was designated as historic under Part 1V of the Ontario Heritage Act the grounds were included in the description:
Legal Description: CON 2 (of) Pt Lot 18. The grounds encompass half a city block. Two acres of land were excluded from the historical designation of 21 Withrow Avenue. (This 1968 photo of the Bell House at 3080 Richmond Road is from the Archives )

"City of Ottawa Individual Designation under Part 1V of the Ontario Heritage Act-Historical or Associative Value because it has direct association with a theme, event, belief, person, activity or institution that is significant to the community; contributes to the understanding of the community; demonstrates the work or ideas of an architect, artist or builder, designer of significance to the community."
In my opinion, the grounds of Kilmorie should be protected by the Ontario Heritage Act because:
1.)  The poet  William Wilfred Campbell was inspired by the landscape surrounding his home, by the nearby Merivale Road and (probably) the Experimental Farm.
2.)  W.W. Campbell spent a few years planting trees and flowers on the grounds of 21 Withrow. More than 100 mature trees will be sacrificed.
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Down the Merivale Road - A poem by W.W. Campbell.
At morning down the Merivale Road
When all the world is June
Of woods and fields the blest abode
And meadow larks atune,
Under the maples in the sun
The world is fair and sweet;
For miles the field and meadows run
A paradise complete.
In fields where daisies blink their eyes,
And molten sunlight sifts,
The buttercup into the skies
Its golden chalice lifts
And out beyond the valley,
The mighty river lies,
Dim, blue and misty, vast and fair,
The lone Laurentians rise.
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There were only a handful of Confederation Poets:
W.W. Campbell
Bliss Carman
Frederick George Scott
Archibald Lampman
Isabella Valancy Crawford
Sir Charles G.D. Roberts
The home of Bliss Carman is a National Historic Place of Canada:

 Confederation Poet Bliss Carman resided at 83 Shore Street, Fredericton, New Brunswick.

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W.W. Campbell was an Officer of the Canadian Club of Ottawa in 1904-1905.

Cultural Heritage Impact Statement regarding 21 Withrow Avenue, presented to the City of Ottawa, October 2017.
Negative impacts:
"The grounds of Kilmorie factored into the writings of Wilfred Campbell. As such, the loss of the expansive grounds surrounding the heritage home could be said to negatively impact the property's historical value." (Page 27/40.)

Southwest court-views up laneway to historic house-views lost.
View of southeast corner of the house-view lost. (Page 28/40.)
The three "gateway" trees are lost as part of the proposed development. (Page 28/40.)