As a young adult, McGrew managed a department store in the Iowa Territory town of Lancaster. In 1857, he relocated to Wyandotte County, Kansas, where he continued to work as a merchant.
McGrew subsequently joined the Republican Party; in 1859 and 1860, he served as a member of the Legislative of the Kansas Territory. In addition, he was twice elected as the mayor of Wyandotte, which is now a part of Kansas City, Kansas.
In 1862, he was elected to the Kansas Senate. Two years later, he won the election for the office of Lieutenant Governor of Kansas. He served in this position as the deputy of Governor Samuel J. Crawford between January 9, 1865 and January 14, 1867 when his term ended.
After the end of his term, he returned to his business as a merchant.
Personal life and death
McGrew was married twice and was survived by several children.[1] He died of sudden heart problems on January 19, 1911 in Kansas City, Kansas.[1]