Buchanan Park is part of the 34.80 hectare (86 acre) property bought in 1854 by the Honourable Isaac Buchanan (1810-1883) - businessman, millionaire, and member of parliament 1857 - 1861, and 1861 to 1863. Buchanan was the first president of Hamilton's Board of Trade, he helped establish the 13th Battalion Volunteer Military Infantry in 1862, and he was a spokesman for the Scots Presbyterian Community in Canada.
The famous Buchanan mansion, Auchmar, sat in the centre of the Buchanan land, at what is now 88 Fennell Avenue West. The manor's name, Auchmar, was taken from Buchanan's home in his native Scotland. He named the land around the house Claremont Heights for the good view from the Mountain brow. Claremont (sometimes spelled "Clairmont") means "clear mountain" in French.
In 1883, after Buchanan's death, Auchmar was sold with 4.05 hectares (10 acres) of land to Captain Trigg, a British officer. One of Buchanan's daughters bought it back from him around 1900, but then sold it to Mr. A. V. Young in 1926. He lived there with his family until September 1943, when it was rented to the Royal Canadian Air Force as a rehabilitation centre. The Hungarian Sisters of Social Service, a Roman Catholic order of nuns based in Stockholm, Saskatchewan, bought the mansion and land from Mr. Young for $32,500 in 1945. Since then they have operated the Holy Spirit Centre from Auchmar for religious retreats.
In 1949 the City bought the rest of the Claremont land for $1 from King George VI. The Claremont property name was changed to Buchanan in 1955. The land came under the control of the Parks Board in 1960. The park's development began the following year.
Both Buchanan Park Public School and St. Vincent De Paul Catholic Elementary School share Buchanan Park at different alternating recesses during the school day.