What event is this quote describing?

"The pinch of the difficulty in the case stated seems to be in the words "forever," coupled with the interdict relating to the Territory N. of L 36° 30'. If the necessary import of these words be that they are to operate as a condition on future States admitted into the Union, and as a restriction on them after admission, they seem to encounter indirectly the arguments which prevailed in the Senate for an unconditional admission of Missouri."

Using the image, explain the significance of this event.

What event is this quote describing?

“A little Yankee woman wrote a book. The single act of that woman’s will caused the war, killed a million men, desolated and ruined the South, and changed the history of the world.”

-Thomas Dixon, a popular Southern author

Using the image, how did this event cause the Civil War?