He graduated from West Point in 1852 as 40th out of 43 cadets, and joined the 2nd United States Infantry.
After the war he remained in the army and rose to the position of Commissary General of Subsistence of the United States Army. When the began in 1861 he was a first lieutenant and Regimental Quartermaster of the 6th United States Infantry. Parker was promoted to captain on August 3, 1861, and was posted to Missouri to serve as a Commissary of Subsistence.
He was sent to western Tennessee in 1862, and was promoted to lieutenant colonel on November 1 that year.
The following month he became the Commissary General for General. Grant´s Army of the Tennessee.
On April 25, 1863, President Abraham Lincoln appointed Hawkins Brigadier General in the United States. Volunteers, with effect from April 13, 1863. However, the United States. Senate returned the nomination to the President on April 1, 1864.
The following day Lincoln renominated Hawkins and the Senate subsequently confirmed the appointment on April 18, 1864.
Hawkins was assigned to command a brigade of the United States Colored Troops (USCT) and the District of Northeastern Louisiana. In April 1864 he assumed command of the 1st Division of the USCT. He and his division distinguished themselves in the assault at the Battle of Fort Blakely on April 9, 1865, which resulted in the capture of Mobile, Alabama. Hawkins was mustered out of the Union Army volunteer service on February 1, 1866.
In the wave of the mass promotions at the end of the war Hawkins was promoted to the brevet grade of major general in both the United States. Volunteers and the regular army.
Hawkins stayed in the army and reverted to his regular rank of captain in the Subsistence Department. He served in a number of postings and received a series of promotions.
To major on June 23, 1874. To lieutenant colonel on September 3, 1889.
And colonel on March 12, 1892.
He was appointed Commissary General of Subsistence of the United States. Army with the rank of brigadier general on December 2, 1892. And remained in this position till he resigned on September 29, 1894 aged 64.