I have discovered that Benjamin Franklin Willis, one of the sons of Isaac Willis, went to Marshall Missouri on a wagon train in 1852 with apparently a great number of Willis, Gordon and Garnett cousins. “Anna Garnett Willis, who came to Saline County with a wagon train of people from Culpeper County, Va., around 1852.” Apparently 1852 was one of the busiest years for westward expansion. 

I found a page with a few bios, and there is some information of others that are listed on this site– these apparently from a book titled “History of Saline County, Missouri 1881“. This is about one half generation before John Milton Willis headed west.

In the book, Owen Thomas Willis is credited as being one of the first settlers in the area of Marshall Township.

Owen Thomas Willis, P. O., Slater. Was born in Culpepper county, Virginia, February 20, 1821, where he was raised and educated, and assisted on his father’s farm until his sixteenth year, then lived with his grandfather, Isaac Willis, and managed his business for twelve years. His father, Joshua Willis, and his mother Ava Willis, formerly Garnett were both natives of Culpepper county, Virginia. He was married December 10, 1844, to Miss Sarah Ann Garnett, daughter of Larkin and Elizabeth Garnett, of Culpepper county, Virginia. He continued farming in Virginia until 1850, when he came to this county, and bought 120 acres of land, two and one-half miles south of the present site of Slater. After building and moving to his farm, he lost his dwelling house by fire, which, with its contents were valued at $1,000. After this, he sold out to his uncle, Bobert Willis, and bought the farm now owned by Reuben Eubank. Selling this to Mr. Eubank, he purchased the farm he now lives on, adjoining the town of Norton on the east, containing 160 acres of land. From 1853 to 1866, he ran a saw mill, six miles east of Miami. Mr. Willis’ children are as follows: Evelyn P., now Mrs. David C. Morrison, of Saline county; Alice, now Mrs. Theodore Haynes, of Slater; Oswald T., Ida B., now Mrs. E. H. Head of Quincy, Illinois; Harry C., William P., Melbourne, E., Price, Owen Shelby, and Sarah E., all living. Mr. Willis has been a member of the Baptist Church since his eighteenth year, and has been connected with Bethel Church [This being one of the two churches where Russel Holman Preached] for over twenty years.

I was especially excited to read the below, as R H Willis has turned up in many of the documents and maps I’ve been looking through over the years. I’m glad to get a bio on him, as well as understand that he is definitely, in fact, one of the Culpeper Willises.

Robert H. Willis, P. O., Marshall. Was born in Culpepper county, Virginia, on the 15th of December, 1837, where he was reared and educated. In 1860, he came to Missouri, and settled in Saline county. In 1861, he joined Capt. Ed. Browns’ company, in the M. S. G. and served six months, the time of enlistment. In December, 1861, he started south with Robinson’s body of recruits, and was captured with them December 19, 1861, on Blackwater, taken to St. Louis, and then to Alton, Illinois, where he remained three months; was then released, on taking the oath, and returned home. In 1864, as Gen. Price’s army passed through Saline, Mr. Willis again enlisted in the Confederate service, in Gen. Marmaduke’s escort company; remained in the service to the end of the war, and surrendered in 1865, at Shreveport. He participated in the battles of Wilson’s Creek, Booneville, Dry Wood, and Lexington. After the war, he settled down on the farm, northeast of Marshall, which he soon after purchased, and resided there until 1875. In 1874, he was elected sheriff of Saline county, and in 1875, moved into Marshall, the county seat, to assume his official duties. Mr. Willis is a democrat, and was again elected sheriff, in 1876. In 1879, Mr. Willis engaged in the grocery business, in Marshall, with Mr. Ben Naylor, until 1881, when Naylor sold out to Wm. Nordyke, and the firm is now Willis & Nordyke. They do a leading business in their line. In 1861, Mr. Willis married Miss Mary E. Cox, daughter of Jesse Cox, a lawyer and an old settler of this county. They have had ten children, eight of whom—two sons and six daughters—are living. Mr. Willis came to Saline poor, but by his industry and management is now in easy circumstances.

This is a bio of E P Garnett’s brother in law. This couple is mentioned in the article linked above. The home that Anna Garnett build with her husband at the age of 26 is still standing. 

WILLIAM PHILIP CASEBOLT, P, O,, Slater. Mr. W. P. Case-
bolt, postmaster of Slater, was born Februar}- 1.5, 1842, in Pocahontas
count}-, Virginia. His father, William Casebolt, was a native of Poca-
hontas county, Virginia, and his mother, Mrs. Ellen Casebolt, formerl}-
Lowe, a native of Braxton county, Virginia. He came to Saline county,
Missouri, with his parents, in 1844, and settled near Miami, where he was
educated. At the age ot’ seventeen years, he engaged as clerk in a
general store in Carrollton, Missouri. In the year 1865, he moved to
Vienna, Maries county, Missouri, and engaged in business. March 4, 1868,
he married Miss Roberta Anderson, daughter of Thomas and Mira
Anderson, of Tennessee. Two children were born to them, and both died
very young. Mrs. Casebolt died on the 13th of February, 1873. In March,
1875, he opened a general store at Petra postoflice. Saline county, and in
1876, was appointed postmaster. In September, 1878, he removed to
Slater, continuing as postmaster, and his business, and building the first
store-house, southwest corner of Main and Front streets, which was
burnt in January, 1881. In the summer of 1879, he disposed of his mer-
cantile stock, and has since given his entire attention to the duties of the
postoffice. In 1879, he built a two-story brick building, with metal roof,
on the east side of Main street. Mr. Casebolt was one of the first citizens
of the present city of Slater, and has aided not a little, by his energy and
enterprise, in its rapid growth, Mr. Casebolt was married, December
25, 1.S79, to Miss Celia Helen Graves, daughter of the late Edward
D. Graves and Martha Ann Graves, formerly Garnett, of this county.

THOMAS GARNETT, deceased. Was born in Culpepper county,
Virginia, in 1810. His early life was spent on a farm and in acquiring an
education in the public schools of his native county. While in Virginia, after
becoming of age, he was engaged in farming, on a grand scale. Was married to
Miss Lucy H. Gordon, of same county, by whom he had nine chil-
dren, seven of whom are living: Anna M., Lucy H., wife of Jas, A.Jordan*
A. C, Laura V., wife of Giles R. McDaniels; T. T., Edmonia J., Joseph
H. In 1852 Mr.Garnett moved to this state and count}-, locating where
his son, A. C, and widow, now reside, on a splendid farm, well adapted to
the raising of all kinds of produce, or stock. Mr. A. C, who now man-
ages the farm, makes a specialt}^ of handling fine stock. The subject of
this sketch died in 1880, having been an active and consistent member of
the Missionary Baptist Church for forty-five years, acting in the capacity
of deacon for several years previous to his death. He died at the ripe age
of seventy years, living the full time allotted to man, leaving behind him a
record of which his descendants may well be proud.

GEORGE WILLIS, P. O., Orearville. Was born in Orange county,
Virginia, June 14, 1834, where he was reared and educated. His father,
Joshua Willis, was a native of Madison county, Virginia, and a farmer.
He was married to Ara Willis, a native of Culpepper county, Virginia,
and daughter of Isaac Willis. They had seven children, five of which
are living: Owen T., Benj. F., George, Mrs. Betty T. Lewis and Mrs.
Mary Ish. Joshua Willis died and was buried in Culpepper county, Vir-
ginia; his wife survived him, died and was buried at Mt. Horeb, in Saline
county, in 1865. George, the fourth son, after stopping school, devoted
his time to the management of his mother’s business on the farm. In the
fall of 1857, he, wath his mother and family, moved west, settling in Saline
county, Missouri, where two of his brothers had already located some
years previous. They traveled by land in wagons, and brought some
twenty or thirty slaves with them. They first settled on what is now
known as the Richard Durrett farm, two miles south of the present city
of Slater, where he farmed until 1859. In April, 1859, he was married to
Miss Margia Ish, of Saline county, a daughter of W. L. Ish. They have
two children: Ortha L. and Etha G.; and in the same year he moved to
the farm on which he now resides, five and one-half miles south of Slater,
where he owns eighty-eight acres of first-class land. In the fall of 1864,
he enlisted in company G, Williams’ regiment, Shelby’s division, as a pri-
vate, and was in the battles of Independence, Big and Little Blue, West-
port and near Ft. Scott. He was discharged in 1865, and returned to his
farm.
In the same book, there is a history of the Rehoboth Church, which was moved, and is now the current Slater Baptist Church:

CHURCHES IN SLATER.
BAPTIST CHURCH.

This church was formerly called Rehoboth Church, and the house of
worship was located half a mile north of town, but on the building of the
town the old structure was taken down and the material worked into the
new church at Slater. Rehoboth Church was organized September 1,
1850. The original members were Daniel Hickerson, W. W. Field, W.
E. Thomson, R. Y. Thompson, R. Johnson, Willis Holloway, B. Hamp-
ton, I. N. Graves, Claiborne Hill, Maria Hickerson, Francis Hickerson,
Francis Hampton, Lucy T. Thompson, Anna L. Hampton, Lucy A.
Thompson, Lucy A. Field, Martha Johnson, Rachel Hufi. The old
Rehoboth church was built in 1850; the new (Baptist Church of Slater)
in 1880. The old church building cost $2,000. Noah Flood dedicated it
on the fifth Sabbath of July, 1853; Rev. W. Pope Yeaman dedicated the
new one August 29, 1880. Rev. Thos. Fristoe was called as first preacher
of the old organization, November 1, 1851. Jos. S. Conners was first pastor
of the new. The present membership is about one hundred. During the
war an association was being held at Rehoboth. The militia arrested all
of the ministers present and put them under bonds.

The question remains: Why did some of the Garnetts arrive in Saline in 1840, and many Garnetts, Gordons and Willises show up together, on a wagon train, in 1852?!