From 1972
Canadian domestic letter rates increased from 8 cents to 46 cents in the last quarter of the twentieth century. This post looks at the first weight step rate changes from 1972.
(Domestic post cards have been treated as letters since November 1, 1968.)
8 cents : January 1, 1972 - August 31 1976

Lawrence Park Collegiate, Toronto, M1P 4T0 to Toronto, May 6, 1976
8 cents letter rate
10 cents : September 1, 1976 - April 31, 1977

Conestogo to Waterloo, September 8, 1976
10 cents letter rate
12 cents: March 1, 1977 - March 31, 1978

Parry Sound to Toronto, April 5, 1977
12 cents letter rate
14 cents : April 1, 1978 - March 31, 1979

London, March 6, 1979
14 cents letter rate
17 cents (up to 1 ounce) :
April 1, 1979 - June 30, 1979

Ottawa (House of Commons) to Welland, May 9, 1979
17 cent letter rate for one ounce
17 cents (up to 30 grams) :
July 1, 1979 - December 31, 1981
Letter weights were now measured in grams.

Mount Bridges to London, Ocotber 19, 1981
17 cents letter rate for 30 grams
30 cent : January 1, 1982 - February 14, 1983
"A" Stamp
Canada Post anticipating it would increase the letter rate from 17 cents but unsure what the change would be printed stamps with the Letter "A" without denomination. The "A" stamps were issued on December 29, 1981, with a value of 30 cents. The 30 cent denominated stamps were issued on May 11, 1981.

Toronto to Weston, March 17, 1982
30 cents letter rate
"A" stamp used in period

Fort Erie to Guelph, February 8, 1983
30 cents letter rate
32 cents : February 15, 1983 - June 23 1985

Ottawa (Senate Post Office) to Montreal, April 12, 1984
32 cents letter rate

Kentville to Niagara Falls, August 30, 1984
8 cent booklet stamps paying the 32 cents domestic letter rate
34 cents : June 24, 1985 - March 31, 1987

Ottawa to Outremont, July 26, 1986
34 cents letter rate
36 cents : April 1, 1987 - December 31, 1987

Ingersoll to Kitchener, December 8, 1987
36 cents letter rate
37 cents : January 1, 1988 - December 31, 1988

Port Hope to Cobourg, December 22 , 1988
38 cents : January 1, 1989 - December 31, 1989

Truro to Toronto, October 10, 1989
38 cents letter rate
39 cents : January 1, 1990 - December 31, 1990

Willowdale to Hamilton, December 19, 1990
39 cents letter rate
40 cents : January 1, 1991 - December 31, 1991

North Bay to Toronto, June 6, 1991
40 cents letter rate
42 cents : January 1, 1992 - December 31, 1992

Stratford to St. John's, September 11, 1992
42 cents letter rate
43 cents : January 1, 1993 - July 30, 1995

Chester to Georgetown, August 22, 1994
43 cents letter rate
45 cents : August 1, 1995 - December 31, 1998

Toronto (M4L 3T0) to Don Mills, May 9, 1996
45 cents letter rate
46 cents : January 1, 1999 - December 31, 2000

Squamous to Mississauga, August 10, 1999
46 cents letter rate to end the 20th Century
47 cents : January 1, 2001 - January 13, 2002

Canada V6B 3A0 (Vancouver) to Vancouver, May 29, 2001
47 cents domestic first weight postal rate
48 cents : January 14, 2002 - January 13, 2004

NATO Forces, CFPO 5048 Casteau, Belgium, July 30, 2003
48 cents first weight surface postal rate
49 cents : January 14, 2004 - January 16, 2005

Canada V6B 3A0 (Montreal) to Lancaster, September 27, 2004
49 cents domestic first weight postal rate