He was born in Gallatin County, Illinois, on the Ohio river, between Flynn's and Ford's Ferry where his father William Baley had a farm.

When the Black Hawk War broke out in 1832, Gillum and his older brother Caleb enlisted in the Illinois Mounted Militia where he was elected a sergeant despite being only 19 at the time.

[2][3] After his wife's death, Baley returned to Missouri, initially settling in Jackson County where he farmed and raised livestock and in late 1836 married Permelia Eleanor Myers.

In addition to running his farm, Baley also served as a Methodist lay preacher and rode circuit as a justice of the peace for the county despite having only studied law informally.

In mid-May while resting at Cottonwood Creek, near present-day Durham, Kansas, they were joined by a party led by Leonard Rose which had left Iowa in April and also intended to travel to California via the Santa Fe Trail.

When the combined party reached Albuquerque, New Mexico, they decided to attempt the final stretch to California via Beale's Wagon Road, at the time little more than a rough trail.

He built a house and started a cattle and dairy farm in the area now known as Bailey (or Baley) Flats which lay at the conjunction of three forks of the Chowchilla River.

He also filed a claim with the Senate Committee on Indian Depredations seeking reparation for the losses suffered in the 1858 Mojave attack on the Rose–Baley Party.

[8] Baley appears as a character in the 1995 children's novel Sallie Fox: The Story of a Pioneer Girl which was based in part on the diary of John Udell, a member of the Rose–Baley Party.

The book is a semi-fictionalized biography of Sallie Fox who as a twelve-year-old child had also travelled with the Rose-Baley Party, surviving both the Mojave attack which killed her stepfather and the trek back to Albuquerque during which her half-brother died.