Michael Kelly Lawler, a volunteer militia soldier in the Black Hawk War (1831–32), an officer in the United States Army in both the Mexican–American War and the American Civil War, is born on November 16, 1814, in Monasterevin, County Kildare. As a brigadier general in the American Civil War, he commands a brigade of infantry in the Western Theater and serves in several battles.

Born to John Lawler and Elizabeth Kelly, they move to the United States four years later and settle initially in Frederick County, Maryland. In 1819, they move to rural Gallatin County, Illinois. On December 20, 1837, Lawler marries Elizabeth Crenshaw. He receives an appointment as a captain in the Mexican-American War and commands two companies in separate deployments to Mexico. He first leads a company from Shawneetown, Illinois that guards the supply route from Veracruz to General Winfield Scott‘s army. After the fall of Veracruz his company is discharged. He makes a visit to Washington after which he is asked by Illinois Governor Thomas Ford to organize a company of riflemen. He serves in the campaign to take Matamoros, Tamaulipas.

Lawler then returns to his farm in Illinois, where he is residing at the outbreak of the American Civil War. He establishes a thriving mercantile business, dealing in hardware, dry goods, and shoes. He studies law, passes his bar exam, and uses his legal license to help the claims of Mexican War veterans.

In May 1861 Lawler recruits the 18th Illinois Volunteer Infantry Regiment and is appointed as its first colonel. His time in command of the regiment in Kentucky and Tennessee is controversial and an “ordeal.” He is wounded during the Battle of Fort Donelson. In November 1862 he is commissioned as a brigadier general, and commands a brigade in the Second Division of the XIII Corps. He fights with distinction in the Vicksburg campaign in 1863. He leads his men in the battles of Port Gibson, Champion Hill, Big Black River Bridge, and the May 22, 1863, general assault on Vicksburg, Mississippi, where troops under his command are the only Union forces to enter the Confederate works at the Railroad Redoubt where they plant the United States flag.

Following the surrender of Jackson, Mississippi, the XIII Corps is split up and divided among other operations in the Western Theater. For the rest of the war, Lawler serves as commander of the 1st Division, XIII Corps in Louisiana in the Department of the Gulf, taking command of the division during the disastrous Red River campaign and leading it on an expedition in June 1864 to secure a crossing of the Atchafalaya River used by Confederate forces.

In the omnibus promotions at the end of the American Civil War, Lawler receives a promotion for distinguished service to major general in the Union army backdated from March 13, 1865. After mustering out of the army in 1866, he returns home and resumes his legal practice and farming near Shawneetown, Illinois.

Lawler dies in Shawneetown on July 22, 1882, and is buried in the Lawler Family Cemetery near Equality, Illinois, at the rear of the Old Slave House property.

A memorial to Lawler stands in Equality, Illinois. He also is honored with a marble bust in Vicksburg National Military Park in Vicksburg, Mississippi. Chicago renames a street to Lawler Avenue in his memory.