How and why did Reconstruction end?
The Compromise of 1876 ultimately ended Reconstruction. See below.
Before looking at the end of Reconstruction, it is important to know what Reconstruction was. After the Civil War came to a close, the North wanted to bring the South back into the Union. However, different politicians came out with different ways to do so. The plan that passed was that of military districts, created by Radical Republicans. This issued that the South be divided into 5 "military districts," each governed by a Republican governor. The South despised this.
Now let's look at what actually ended this Reconstruction idea of merging the South with the North/Union. It was the election of 1876 and Samuel Tilden ran for the Democratic party and Rutherford B. Hayes ran for the Republican party. When the election results came in, they were disputed, so it went to Congress. The Republicans negotiated and bribed Southern Democrats to vote for Hayes, but Southern Democrats had one condition: that the Republicans end military districts in the South. Republicans at this time were desperate, so they struck the deal, also known as the Compromise of 1876.
This ultimately ended Reconstruction and would eventually lead to Southerners enacting Jim Crowe laws and other oppressive movements.
Hope this helps!