McEwan was born in Paterson, New Jersey on February 26, 1854. He attended the public schools and became a civil engineer. He attended the law department of Columbia Law School was admitted to the bar about 1885 and commenced practice in New York City and Jersey City, New Jersey. He was the assessor of the fourth district of Jersey City in 1886 and 1887. He was secretary to Dr. Morgan Dix, rector of Trinity Church in New York City from 1886-1906. He was tax assessor of Jersey City in 1887 and 1888, and was the United States commissioner and chief supervisor of elections for the district of New Jersey from August 1892 to October 1893. McEwan was a delegate to and secretary of every Republican convention of New Jersey and Hudson County from 1877-1896, and was secretary of the Hudson County Republican general committee from 1878-1893. He served as a delegate to the Republican National Convention in 1892 and 1896. He was a member of the New Jersey General Assembly in 1893 and 1894 and served as Republican leader in 1894.
After leaving Congress, he resumed the practice of law and also engaged in banking in West Hoboken, New Jersey, from 1904 until July 1, 1924, when he retired. He was controller of Jersey City 1906 and 1907. He died in Jersey City on September 11, 1926, and was interred in Flower Hill Cemetery in North Bergen, New Jersey.