Actually, there were seven states are the start:
South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, and Texas.
So the first flag had 7 stars.
Then Virginia, Arkansas, Tennessee, and North Carolina joined.
Missouri and Kentucky were represented by partisan factions from those states (states had dual governments).
West Virginia broke away from Virginia was admitted to the Union during the US Civil War.
Nevada also joined the Union during the US Civil War as well.
Kansas became a state 3 months before the opening battle of the US Civil War.
Ken