Question: Geary County, Kansas is named after what Civil War union general? 

Context paragraphs:
Stevens County, Minnesota: Stevens County is a county located in the U.S. state of Minnesota.  As of the 2010 census, the population was 9,726.  Its county seat is Morris.  The county was named for the Civil War Union general Isaac Stevens; it was named for him in 1862, seven years after a legislative clerical error denied him that honor in 1855 for what became Stearns County.

Fort Griffin: Fort Griffin, now a Texas State Historic Site, was a US Cavalry fort established 31 July 1867 by four companies of the Sixth Cavalry, U.S. Army under the command of Lt. Col. S.D. Sturgis, in the northern part of West Texas, specifically northwestern Shackelford County, to give settlers protection from early Comanche and Kiowa raids.  Originally called Camp Wilson after Henry Hamilton Wilson, a recently deceased lieutenant, it was later named for Charles Griffin, a former Civil War Union general who had commanded, as" de facto "military governor, the Department of Texas during the early years of Reconstruction.

Sprague, Washington: Sprague is a city in Lincoln County, Washington, United States.  The population was 446 at the 2010 census.  The town was plotted in 1880 and named for former American Civil War Union general John Wilson Sprague.

Geary County, Kansas: Geary County (county code GE) is a county located in the U.S. state of Kansas.  As of the 2010 census, the county population was 34,362.  Its county seat and most populous city is Junction City.  The county is named in honor of Governor John W. Geary.

Paul Ambrose Oliver: Paul Ambrose Oliver (July 18, 1831 – May 17, 1912) was an American explosives inventor, American Civil War Union Army captain and staff officer who was appointed to the brevet grade of brigadier general and Medal of Honor recipient.  He was born on the "Louisiana", his father's merchant ship, during one of its voyages in the English Channel.  Before the Civil War, he worked as a shipping merchant.

Winfield Scott Hancock: Winfield Scott Hancock (February 14, 1824 – February 9, 1886) was a career U.S. Army officer and the Democratic nominee for President of the United States in 1880.  He served with distinction in the Army for four decades, including service in the Mexican–American War and as a Union general in the American Civil War.  Known to his Army colleagues as "Hancock the Superb", he was noted in particular for his personal leadership at the Battle of Gettysburg in 1863.  One military historian wrote, "No other Union general at Gettysburg dominated men by the sheer force of their presence more completely than Hancock."  As another wrote, "his tactical skill had won him the quick admiration of adversaries who had come to know him as the 'Thunderbolt of the Army of the Potomac'."  His military service continued after the Civil War, as Hancock participated in the military Reconstruction of the South and the Army's presence at the Western frontier.

Fort Whipple, Arizona: Fort Whipple was a U.S. Army post which served as Arizona Territory's capital prior to the founding of Prescott, Arizona.  It was named after Amiel Weeks Whipple, a Civil War Union General.  The post was founded by Edward Banker Willis in December 1863 in Del Rio Springs, but was moved in May 1864 to a miner's tent settlement called Granite City (also Granite Dells, Gimletville), which was on higher ground, had better access to lumber, and the military could better protect miners.  The capital was placed 2 miles south in the new city of Prescott founded in 1864.

St. Augustine in the American Civil War: During most of the American Civil War the Florida city of St. Augustine was under Union control.  Its Confederate history was exceedingly brief.  One Union general and one Confederate general were natives of the Ancient City.  Many officers on both sides (including Union General William T. Sherman and Confederate General Braxton Bragg) had previous military experience in St. Augustine, particularly during the Second Seminole War.  The city's historic (and endangered) Sea Wall was built in the 1830s, 1840s and 1850s by West Point engineers who went on to design military fortifications for both sides in the Civil War.  Many black Union soldiers either came from St. Augustine, or settled there after the war, providing a leadership cadre for the community known as Lincolnville that was established in 1866.  Many of the city's old cemeteries feature the distinctive marble tombstones marked "USCT"--United States Colored Troops.

Henry Warner Slocum: Henry Warner Slocum, Sr. (September 24, 1827 – April 14, 1894), was a Union general during the American Civil War and later served in the United States House of Representatives from New York.  During the war, he was one of the youngest major generals in the Army and fought numerous major battles in the Eastern Theater and in Georgia and the Carolinas.  While commanding a regiment, a brigade, a division, and a corps in the Army of the Potomac, he saw action at Bull Run, the Peninsula, South Mountain, Antietam, Chancellorsville, and Harpers’ Ferry.  At Gettysburg, he was the senior Union General in the Field.  During the battle, he held the Union right from Culp’s Hill to across the Baltimore Pike.  His successful defense of Culp’s Hill was crucial to the Union victory at Gettysburg.  After the fall of Vicksburg, Slocum was appointed military commander of the district.  Slocum participated in the Atlanta campaign and was the first commander to enter the city on September 2, 1864.  He then served as occupation commander of Atlanta.  Slocum was appointed the commander of the left wing of Sherman’s march through Georgia and the Carolinas, commanding the XIV and XX Corps, comprising the Army of Georgia.  During this campaign, he captured the capitol of Georgia, Milledgeville, and the seaport of Savannah.  In the Carolinas campaign, Slocum’s army saw victories in the battles of Averasborough and Bentonville, North Carolina.  The March to the Sea and the Carolinas campaign were crucial to the overall Union victory in the Civil War.  After the surrender of Confederate forces, Slocum was given command of the Department of Mississippi.  Slocum declined an appointment in the postwar Army.  He was a successful political leader, businessman and railroad developer.

John W. Geary: John White Geary (December 30, 1819February 8, 1873) was an American lawyer, politician, Freemason, and a Union general in the American Civil War.  He was the final alcalde and first mayor of San Francisco, a governor of the Kansas Territory, and the 16th governor of Pennsylvania.

Supporting paragraphs: Geary County, Kansas John W. Geary
Answer: John W. Geary