The Upper South refers to Delaware, Maryland, Virginia, North Carolina, Tennessee and Kentucky - slave states that did not initially join Confederacy at start of Civil War but later joined due to various reasons including geographical location and economic factors.
congrats on reading the definition of Upper South. now let's actually learn it.
Lower South: These were seven original Confederate states which seceded before or shortly after Battle of Fort Sumter. They include Alabama, Florida, Georgia, Louisiana, Mississippi, South Carolina and Texas.
Border States: These were slave states that didn't secede from Union during Civil War. They include Delaware, Kentucky, Maryland, and Missouri.
Compromise of 1850: This was a package of five separate bills passed by the U.S. Congress in September 1850 to defuse a political confrontation between slave and free states on status of territories acquired in Mexican–American War.