Atchison County, one of the northeastern counties of the state, was created by the first territorial legislature in 1855, with the following boundaries, "Beginning at the southeast corner of the county of Doniphan; thence west twenty-five (25) miles; thence south sixteen (16) miles; thence east to the Mississippi (Missouri) river; thence up said river to the place of beginning." The county was named in honor of David R. Atchison, United States senator from Missouri, and the town of Atchison was made the county seat. In 1868, the boundaries of the county were redefined as follows: "Commencing at the southeast corner of Doniphan county; thence with the southern boundary of Doniphan county, to the township line between townships 4 and 5 south; thence west with the said township line between townships 4 and 5 south, to the range line between ranges 16 and 17 east; thence south with said range line, to the southwest corner of section 19, of township 7 south of range 17 east; thence east with the section lines to the intersection with the west boundary line of the State of Missouri; thence north with said boundary line of the State of Missouri, to the place of beginning."

Atchison county is in the second tier of counties south of the Nebraska state line and has an area of 423 square miles. It is bounded on the north by Brown and Doniphan counties, on the east by Doniphan county and the Missouri river, which divides it from the State of Missouri, on the south by Leavenworth and Jefferson counties and on the west by Jackson county. It is divided into the following townships: Benton, Center, Grasshopper, Kapioma, Lancaster, Mount Pleasant, Shannon and Walnut. The surface of the county is gently undulating prairie, except along the Missouri river where it breaks into prominent bluffs. The average width of the valleys is from a quarter of a mile to a mile and a half and these constitute about one-eighth of the area. Timber is found along all the streams, the principal varieties being black walnut, burr-oak, black and white oak, hickory, red and white elm and honey-locust. Besides the Missouri river, which forms the eastern boundary, there is the Delaware river, which flows across the southwest corner, Stranger creek in the center of the county, and Independence creek which forms a part of the northeastern boundary. A mineral spring, said to have medicinal properties, is at Arrington in the southwest. Limestone and sandstone are plentiful; a rich vein of coal, averaging 3 feet or more in thickness, has been found just outside the corporate limits of Atchison; and there an abundance of clay for making vitrified brick.

The territory now embraced within the limits of the county originally formed a part of the Kickapoo reserve, established by the treaty of 1833, with the exception of the southwest corner which was a part of the Delaware reserve and outlet, established by the treaty of 1831. These lands were ceded, under certain conditions, to the general government in 1854 and opened to settlement.

The first white men to visit the county now embraced within the boundaries of Atchison county were French traders, who passed up the Missouri river during the first quarter of the eighteenth century. French trade was well established upon the Missouri river by 1764 and the eastern part of Atchison county known to the traders. Lewis and Clark passed along the eastern boundary on their expedition in 1804 and spent some time in exploring the banks of the Missouri river. In 1818 the first military post established by the United States government in what is now Kansas was built on the Isle au Vache (q. v.), or Cow island. It was known as Cantonment Martin.

In 1833, the Methodist Episcopal church established a mission among the Kickapoos, located in what is now the northwestern corner of the county near Kennekuk. The first white man to locate permanently and erect a home is supposed to have been a Frenchman named Pensoneau, who married a Kickapoo Indian and settled on the banks of Stranger creek in 1839.

As soon as it was definitely known that Kansas Territory would be opened to settlement, the pro-slavery party in Missouri began to lay plans by which the county would be settled by men of their political faith. Some of the first settlers were a party from Iatan, Mo., who took claims in the vicinity of Oak Mills in June, 1854, but the actual settlers and the real founders of the county and city of Atchison did not enter the territory until the next month. (See Atchison.) Some of the setlers[sic] of Atchison county in 1854 were James T. Darnall, Thomas Duncan, Robert Kelly, B. F. Wilson, Henry Cline and Archibald Elliott. The county was surveyed into townships in 1855, and into sections in fall of that year. One of the earliest, and practically the only free-state settlement in Atchison county, was started in Center township in Oct., 1854, by Caleb May. The town of Pardee was laid out in the spring of 1857 and named in honor of Pardee Butler, a minister of the Christian church and one of the ardent free-state advocates. Monrovia was laid out in 1856 and Lancaster in 1857.

About five miles west of Atchison the old military road ran north and south across the county and there the citizens of Atchison sold land to the Mormon emigrant agents. For years quite a settlement of them was to be found there, although they rarely remained long. The roads west through the county became deeply worn into ruts by the thousands who passed over them. The overland stage route to California ran west through Atchison county into Franklin county; the Butterfield overland dispatch to Denver started from Atchison, as did also the parallel roads to the gold fields. Thousands passed along these well known highways, but there were few settlers in Atchison county from any state except Missouri. In fact they so predominated that the people who advocated free-state principles did not dare let it be known. The first open trouble between a free-state man and the pro-slavery men in Atchison county occurred in 1855, when J. W. B. Kelley, a free-soiler in politics, made offensive remarks about slavery, and particularly about a female slave who was supposed to have committed suicide. Her owner in consequence inflicted bodily chastisement upon Kelley. A large number of the citizens of the town adopted resolutions ordering Kelley, under penalty of further punishment, to leave the town. They also ordered all emissaries of the abolition societies to leave or their reward would be "the hemp." It was resolved to "purge" the county of all free-state people. All persons who refused to sign the resolutions were to be regarded and treated as abolitionists. (See Butler, Pardee.)

The bold attitude of the free-state settlers of Lawrence increased the fire of political feeling among the pro-slavery men of Atchison and added to their martial ardor. In the Wakarusa War (q. v.) an Atchison company took a promient[sic] part in the siege. Other companies were in the battle of Hickory Point.

The pro-slavery leaders of Atchison, who dominated the politics of the county, had so terrorized the other settlers that up to the summer of 1857 the free-state men in the county had formed no organization. Meetings had been held outside of Atchison, however, and during the summer a society was formed at Monrovia with F. G. Adams as chairman. About the same time the Atchison Town company disposed of a large part of its property interests to the New England Aid company, and the Squatter Sovereign, the first newspaper in the county, originally a strong pro-slavery organ, was turned over to S. C. Pomeroy, who, with F. G. Adams and Robert McBratney, turned it into the Champion, a free-state sheet.

As the town company had made such a compromise in politics for the sake of business, Mr. Adams thought that the free-state men could go still further, and advertised that Gen. James H. Lane would speak in Atchison on Oct. 19. A number of reliable free-state men came up from Leavenworth to see fair play, as the opposition had declared that Lane should not speak. Mr. Adams was assaulted in the morning and feeling ran so high with both parties parading the streets armed, that it was decided to postpone the meeting. Lane was turned back before entering the city and thus further trouble was avoided.

Atchison county was the first county in Kansas to secure railroad connections. The St. Joseph & Atchison road was completed to Atchison in Feb., 1860. This was most important for the county and city, as it removed from Leavenworth much of the trade that had formerly gone there, and secured the shipment of all the government freight to the western military posts. It also removed the starting point of the overland mail to Atchison from St. Joseph. At the present time the county's shipping facilities are provided by two lines of the Missouri Pacific, one entering on the western border, the other on the northern, converging at Atkinson a branch line of the Chicago, Burlington & Quincy, which enters the county in the northeast and terminates at Atchison; a line of the Atchison, Topeka & Santa Fe, has its terminus at Atchison, with a branch from Hawthorn to Kansas City. The Chicago, Rock Island & Pacific, Hannibal & St. Joseph and Kansas City, St. Joseph & Council Bluffs railroads cross the Missouri river from Missouri to Atchison and connect that city with the east and the Leavenworth, Kansas & Western railroad crosses the southeast corner.

The county commissioners of Atchison county were elected by the territorial legislature, and Gov. Woodson signed their commissions on Aug. 31, 1855. They met and organized on Sept. 17 at the house of O. B. Dickerson in Atchison, the members present being William J. Young, James M. Givens and James A. Headley, probate judge. William McVay had been appointed sheriff previous to this meeting, at which time the following officers were appointed by the board: Ira Morris, clerk and recorder; Samuel Walters, assessor; Samuel Dickson, treasurer. The county was divided into three townships: Grasshopper, Mount Pleasant and Shannon. The next day Eli C. Mason was appointed sheriff in place of McVay, who resigned, and Dudley McVay was chosen coroner. Voting precincts were established for each township in preparation for the election of a delegate to Congress, which was set for the first Monday of October. The town company of Atchison had offered to donate "Block 10" for the location of the county court-house. The offer was accepted and in October the commissioners ordered that this block he made the site of a brick building at least 40 feet square. Fifty lots were sold on May 1, 1856, the proceeds to be used to help in the expense of the building. There was some question as to the permanent location of the county seat, and this was not settled until the election held on the first Monday in Oct., 1858, when Atchison received the majority of votes. Work was then pushed rapidly along and the court-house was completed in 1859. The county jail, adjoining it, was completed about the same time. As the offices in the old court-house grew too crowded with the increasing business, a fine new court-house was erected in the winter of 1896-97. No bonds were issued, the funds to pay for it being secured by three annual direct tax levies, in 1869 the county purchased a poor farm 4 miles south of the city of Atchison, and erected an $8,000 building. This farm has been self-supporting.

When the call came for volunteers at the outbreak of the Civil war, no men were more patriotic than those of Atchison county, which was represented in the First, Seventh, Eighth, Tenth, Thirteenth and First (colored) Kansas regiments; the First Nebraska and the Thirteenth Missouri; and also in the Ninth, Fifteenth and Sixteenth Kansas regiments. Being on the border, Atchison county was liable to raids from the Confederate army and guerrilla bands from across the border, which necessitated the raising of companies of home guards. During the year 1863 the depredations of lawless bands became so annoying that vigilance committees were formed, the members taking an oath to support the Union and to assist in suppressing rebellion. They became an effective auxiliary to the civil authorities in punishing violators of the law.

Atchison, situated in the eastern part of the county on the Missouri river, is the seat of justice as well as the largest and most important town in the county. It is a shipping and jobbing point for a large and rich agricultural territory.

According to the U. S. census for 1910 the population of Atchison county was 28,107. The value of farm products that year, including live stock, was $2,723,570. The five principal crops, in the order of their value, were: corn, $1,112,386; oats, $236,552; hay, $216,282; wheat, $170,850, and the value of live stock slaughtered or sold for slaughter was $600,709.