John Walker Baylor was born at Woodlawn, Bourbon County, Kentucky, around December 1813 to John Walker and Sophia Marie (Weidner) Baylor. His father, an army physician, was the son of Capt. Walker Baylor, who commanded George Washington's Life Guard in the Third Continental Division at the battle of Germantown. Baylor briefly attended Bardstown College in Kentucky and was appointed to the United States Military Academy at West Point on July 1, 1832. He had disciplinary problems there and was once reinstated by President Andrew Jackson. He left in 1833 and studied medicine under his father until the elder Baylor's death in 1835.
He registered at Fort Gibson, Arkansas, under the name Walker Baylor, then joined George M. Collinsworth's volunteers at Matagorda, Texas, on October 5, 1835. He signed an agreement with other members of Collinsworth's company to protect the citizens of Guadalupe Victoria (now Victoria, Texas). He fought at Goliad on October 9 in the capture of La Bahía from a small Mexican garrison. He was a member of Philip Dimmitt's Goliad garrison and fought under James Bowie and James Fannin in the battle of Concepción on October 28. (see goliad campaign of 1835.) On November 21, 1835, he was part of a committee at Goliad assigned to prepare a document expressing the volunteers' defiance of an order from Stephen F. Austin directing Dimmitt to turn over control of the post to Collinsworth. Baylor was in the five-day siege of Bexar on December 5–9, 1835. He signed the Goliad Declaration of Independence on December 20. Dimmitt's command was disbanded in 1836, and Baylor went to San Antonio with either Bowie or Dimmitt.
After the attack on the Alamo began, Baylor was one of four or five couriers sent by William B. Travis to La Bahía to urge Fannin to come to his aid. At Goliad, Baylor became a member of Capt. John (Jack) Shackelford's Red Rovers. He joined Capt. Albert C. Horton's cavalry on March 14 and participated in several skirmishes against Gen. José de Urrea's Mexican cavalry. Horton's troopers were scouting ahead of Fannin's retreating army and so were not captured with the other Texans in the battle of Coleto and consequently were not executed in the Goliad Massacre (see goliad campaign of 1836). Some of the troops, including Baylor, were bitter that Horton did not come to the aid of the beleaguered encampment. Baylor made his way to Houston's army on the Brazos, where he joined William H. Patton's company in Col. Sidney Johnson's Second Texas Volunteer Regiment. He was named drillmaster because of his West Point experience. In the battle of San Jacinto he received a thigh wound that he considered so slight he did not report it. On May 29 he joined a group of mounted rangers under Maj. Isaac Burton. The rangers were sent by Gen. Thomas J. Rusk to patrol the coast and watch for a possible Mexican attack from the sea. At Copano these "Horse Marines" captured three ships bearing supplies for the Mexican army.
On July 25 Baylor drew sixty-four dollars in back pay and went on furlough to the home of his uncle, Robert Emmett Bledsoe Baylor, in Alabama. His wound had become inflamed. He developed a fever and died on September 3, 1836, in Cahaba, Alabama, an unreported casualty of the battle of San Jacinto. He was possibly the only Texan to fight in every major battle of the Texas Revolution. His brothers George W., Henry W., and John R. Baylor became prominent as Texas Rangers, soldiers, and Indian fighters.