Educational public schools, Orillia, Canada, until 14. Apprenticed to trade of carriage painting. Went to California, 1882.
Worked at trade, 1882-1883.
In painting business, Santa Rosa, California, until 1897.
Later learned the trade of carriage painting and worked in Flint, Michigan, and San Francisco, Sacramento, and Santa Rosa, California. He was admitted to the bar by the supreme court of California in 1892 and commenced practice in Santa Rosa, California. Second assistant United States attorney at San Francisco 1901–1904.
First assistant United States attorney 1904–1907.
McKinlay was elected as a Republican to the Fifty-ninth, Sixtieth, and Sixty-first Congresses (March 4, 1905 – March 3, 1911). He was an unsuccessful candidate for reelection in 1910 to the Sixty-second Congress.
He was appointed by President Taft as United States surveyor of customs for the port of San Francisco, California, in 1910. He died in Berkeley, California, December 30, 1914.
He was interred in Sunset Cemetery.
Member 59th to 61st Congresses (1905-1911), 2d California
Married Nannie V. Hendley, of Santa Rosa, California, December 16, 1884.