Question: Who wrote a letter to Orville Browning where he recognized the importance of one of the four slave states that never declared a secession in the Civil War?

Context paragraphs:
King Cotton: "King Cotton" as a slogan summarized the strategy used before the American Civil War of 1861–1865 by pro-secessionists in the Southern States (the future Confederacy) to claim the feasibility of secession and to prove there was no need to fear a war with the Northern States.  The theory held that control over cotton exports would make a proposed independent Confederacy economically prosperous, would ruin the textile industry of New England, and—most importantly—would force Great Britain and perhaps France to support the Confederacy militarily because their industrial economies depended on Southern cotton.  The slogan, widely believed throughout the South, helped in mobilizing support for secession: by February 1861, the seven states whose economies were based on cotton plantations had all seceded and formed the Confederacy (C.S.A.).  Meanwhile, the other eight slave states, with little or no cotton production, remained in the Union.

President Lincoln's 75,000 volunteers: On April 15, 1861, at the start of the American Civil War, the President of the United States, Abraham Lincoln, called for a 75,000-man militia to serve for three months following the bombardment and surrender of Fort Sumter.  Some slave states refused to send troops against their neighboring slave states, with the result that most such states also declared secession from the United States and joined the Confederate States.

Outline of the American Civil War: American Civil War – civil war in the United States of America that lasted from 1861 to 1865.  Eleven Southern slave states declared their secession from the United States and formed the Confederate States of America, also known as "the Confederacy."  Led by Jefferson Davis, the Confederacy fought against the United States (the Union), which was supported by all the free states (where slavery had been abolished) and by five slave states that became known as the border states.

George W. L. Bickley: George Washington Lafayette Bickley (1823 – August 1867) was the founder of the Knights of the Golden Circle, a Civil War era secret society used to promote the interests of the Southern United States by preparing the way for annexation of a "golden circle" of territories in Mexico, Central America, and the Caribbean which would be included into the United States as southern or slave states. Bickley was arrested by the United States government and it was during this time he wrote a letter to Abraham Lincoln expressing his distastes with Lincoln's handling of the government.

Texas secession movements: Texas secession movements principally focus on the secession of Texas during the American Civil War and the activities of organizations that have existed since the 1990s.  The United States Constitution does not address secession of states and the issue was a topic of debate from after the Revolutionary War up until the Civil War, when the Supreme Court ruled, in "Texas v. White," that states cannot secede.  Texas claimed to be a sovereign state for nine years prior to the negotiated annexation with the United States, but its claim was not recognized by Mexico, nor did Texas actually control the entirety of its claimed territory.  This history has affected the state's politics ever since, including its standing in the Confederacy in the Civil War to education and even tourism in the 20th century.  Modern secession efforts have existed in the state at least since the 1990s, focusing first on the Republic of Texas organization founded by Richard Lance McLaren and later on the Texas Nationalist Movement headed by Daniel Miller.

Border states (American Civil War): In the context of the American Civil War (1861–1865), the border states were slave states that did not declare a secession from the Union and did not join the Confederacy.  To their north they bordered free states of the Union and to their south they bordered Confederate slave states.  Of the 34 U.S. states in 1861, nineteen were free states and fifteen were slave states.  Four slave states never declared a secession: Delaware, Kentucky, Maryland, and Missouri.  Four others did not declare secession until after the Battle of Fort Sumter and were briefly considered to be border states: Arkansas, North Carolina, Tennessee, and Virginia—after this, they were less frequently called “border states”.  Also included as a border state during the war is West Virginia, which was formed from 50 counties of Virginia and became a new state in the Union in 1863.

Cooperationists: The Cooperationists were a group formed in the United States in the 1860s.  The group was formed after the Election of 1860.  Following South Carolina's Secession from the Union, the Cooperationists believed that the remaining slave states should secede at once and at the same time, rather than one at a time, as they believed that doing so would impress the federal government with the seriousness of their resolve.  The proposal was rejected, but the Southern States nonetheless seceded in rapid succession.  The following is a list of the states that seceded, including the date on which each state seceded: South Carolina (December 20, 1860), Mississippi (January 9, 1861), Florida (January 10, 1861), Alabama (January 11, 1861), Georgia (January 19, 1861), Louisiana (January 26, 1861), Texas (February 1, 1861), Virginia (April 17, 1861), Arkansas (May 6, 1861), North Carolina (May 20, 1861), and Tennessee (June 8, 1861).

Slave states and free states: In the history of the United States of America, a slave state was a U.S. state in which the practice of slavery was legal, and a free state was one in which slavery was prohibited or being legally phased out.  Historically, all the British colonies had practiced slavery.  The division between slave and free states began during the American Revolution (1775–1783).  Slavery became a divisive issue and was the primary cause of the American Civil War.  The Thirteenth Amendment to the United States Constitution, ratified in 1865, abolished slavery throughout the United States, and the distinction between free and slave states ended.

List of Confederate arsenals and armories: This is a list of Confederate arsenals and armories.  The Confederate States of America was a government set up from 1861 to 1865 by eleven Southern slave states that had declared their secession from the United States.  The Confederate States Army was the army of the Confederate States of America while the Confederacy existed during the American Civil War.  Arsenals and armories in this list were active during the years of the confederacy and during the American Civil War.

Kentucky in the American Civil War: Kentucky was a border state of key importance in the American Civil War.  President Abraham Lincoln recognized the importance of the Commonwealth when, in a September 1861 letter to Orville Browning, he wrote:

Supporting paragraphs: Border states (American Civil War) Kentucky in the American Civil War
Answer: Abraham Lincoln