Which happened first?

a. President Abraham Lincoln issued the Emancipation Proclamation.
b. The battle of Antietam was fought in Maryland.

a. The Civil War began.
b. John Brown led a raid on Garper's Ferry in Virginia.

a. The Supreme Court reached a decision in the case of DRed Scott v. Sanford.
b. The Kansas-Nebreaska Act was passed by Congress.

a. Abraham Lincoln was elected President of the United States.
b. Southern states began to secede from the Union.

a. Rutherford B. Hayes was elected President of the United States.
b. Thh Reconstruction Era ended when federal troops were with drawn from the South.

http://en.wikipedia.org/wiki/Emancipation_Proclamation

http://en.wikipedia.org/wiki/Battle_of_Antietam

http://en.wikipedia.org/wiki/American_Civil_War

http://en.wikipedia.org/wiki/John_Brown's_raid_on_Harpers_Ferry

Those sites give you the first two answers. You can Google the other events to find their dates.

To determine which event happened first in each pair of events, we can use historical knowledge and timeline information. Here are the chronological sequences for each pair of events:

a. President Abraham Lincoln issued the Emancipation Proclamation.
b. The battle of Antietam was fought in Maryland.

The correct order is:
1. The battle of Antietam was fought in Maryland (September 17, 1862).
2. President Abraham Lincoln issued the Emancipation Proclamation (January 1, 1863), after the Battle of Antietam.

a. The Civil War began.
b. John Brown led a raid on Garper's Ferry in Virginia.

The correct order is:
1. John Brown led a raid on Garper's Ferry in Virginia (October 16-18, 1859).
2. The Civil War began (April 12, 1861), after John Brown's raid.

a. The Supreme Court reached a decision in the case of Dred Scott v. Sanford.
b. The Kansas-Nebraska Act was passed by Congress.

The correct order is:
1. The Kansas-Nebraska Act was passed by Congress (May 30, 1854).
2. The Supreme Court reached a decision in the case of Dred Scott v. Sanford (March 6, 1857), after the Kansas-Nebraska Act.

a. Abraham Lincoln was elected President of the United States.
b. Southern states began to secede from the Union.

The correct order is:
1. Abraham Lincoln was elected President of the United States (November 6, 1860).
2. Southern states began to secede from the Union (starting with South Carolina on December 20, 1860), after Lincoln's election.

a. Rutherford B. Hayes was elected President of the United States.
b. The Reconstruction Era ended when federal troops were withdrawn from the South.

The correct order is:
1. The Reconstruction Era ended when federal troops were withdrawn from the South (in 1877, following the 1876 presidential election).
2. Rutherford B. Hayes was elected President of the United States (in the controversial 1876 election, which was resolved in 1877).