Here’s an ad for a taxicab service from the October 14 1936 edition of the Toronto Daily Star:

I looked up Deer Park Livery in the Toronto city directories:
- They are listed in the 1936 directory as Deer Park Garage & Livery Limited at 1365-1371 Yonge Street, which is how they appear in the 1941 and 1946 directories.
- By 1949, the firm had changed hands a couple of times, and was listed as simply Deer Park Livery Limited.
- In 1951, they moved to 811 King West, which isn’t in Deer Park, if you want to get pedantic about it.
- The last directory that Deer Park Livery appears in is 1960.
- I have no way of knowing whether they were Toronto’s oldest livery, but they do appear in the 1915 city directory, so they had been around a while.
A search turned up this ad from the 1929 CNE program.