Childs was born in Pittsfield, Massachusetts, the son and grandson of Revolutionary War veterans.
He graduated from West Point in 1814 and fought in the Niagara campaign during the War of 1812 as an officer of artillery.
He transferred to Winfield Scott's army with the rest of the division and was Worth's chief-of-staff during the Siege of Veracruz.
During the following siege of Puebla Childs repeatedly refused to surrender and was able to successfully repulse the Mexican attacks until a relief force under General Joseph Lane arrived and defeated the besiegers.
He died in his headquarters at Fort Brooke, and was buried at St. Paul's Cemetery in Alexandria, Virginia.