Union General George Armstrong Custer marries Elizabeth Bacon in Monroe, Michigan, while the young cavalry officer is on leave. “Libbie,” as she was known to her family, was a tireless defender of her husband’s reputation after his death at the Battle of the Little Bighorn in Montana in 1876, and her work helped establish him as an American hero.

On February 20, 1864, at the Battle of Olustee, the largest conflict fought in Florida during the Civil War, a Confederate force under General Joseph Finegan decisively defeats an army commanded by General Truman Seymour. The victory kept the Confederates in control of Florida’s interior for the rest of the war.

On February 24, 1864, the first Union inmates begin arriving at Andersonville prison, which was still under construction in southern Georgia. Andersonville became synonymous with death as nearly a quarter of its inmates died in captivity. Henry Wirz, who ran Andersonville, was executed after the war for the brutality and mistreatment committed under his command.

On March 1, 1864, Rebecca Lee Crumpler becomes the first African American woman to earn a medical degree. For much of her career she practiced community medicine in Boston, but in the aftermath of the Civil War she traveled south to treat thousands of formerly enslaved refugees. Crumpler wrote one of the first medical manuals by an African American doctor in the United States—and by a woman.

On March 10, 1864, President Abraham Lincoln signs a brief document officially promoting then-Major General Ulysses S. Grant to the rank of lieutenant general of the U.S. Army, tasking the future president with the job of leading all Union troops against the Confederate Army.

Local hell-raiser Jack Slade is hanged in one of the more troubling incidents of frontier vigilantism.

On March 12, 1864, one of the biggest military fiascos of the Civil War begins as a combined Union force of infantry and riverboats starts moving up the Red River in Louisiana. The month-long campaign was poorly managed and achieved none of the objectives set forth by Union commanders.

During the American Civil War, Major General Nathan Bedford Forrest’s Confederate raiders attack the isolated Union garrison at Fort Pillow, Tennessee, overlooking the Mississippi River. The fort, an important part of the Confederate river defense system, was captured by federal forces in 1862. Of the 500-strong Union garrison defending the fort, more than half the soldiers were African Americans.

On May 8, 1864, Yankee troops arrive at Spotsylvania Court House, Virginia, to find the Rebels already there. After the Battle of the Wilderness (May 5-6), Ulysses S. Grant’s Army of the Potomac marched south in the drive to take Richmond. Grant hoped to control the strategic crossroads at Spotsylvania Court House, so he could draw Robert E. Lee’s Army of Northern Virginia into open ground.

A dismounted Union trooper fatally wounds J.E.B. Stuart, one of the most well-known generals of the South, at the Battle of Yellow Tavern, just six miles north of Richmond, Virginia. The 31-year-old Stuart died the next day.

President Abraham Lincoln writes to anti-slavery Congressional leader Senator Charles Sumner of Massachusetts on May 19, 1864, proposing that widows and children of soldiers should be given equal treatment regardless of race.

Union General Ulysses S. Grant makes what he later recognizes to be his greatest mistake by ordering a frontal assault on entrenched Confederates at Cold Harbor, Virginia. The result was some 7,000 Union casualties in less than an hour of fighting.

During the Civil War, Ulysses S. Grant’s Army of the Potomac and Robert E. Lee’s Army of Northern Virginia collide for the last time as the first wave of Union troops attacks Petersburg, a vital Southern rail center 23 miles south of the Confederate capital of Richmond, Virginia. The two massive armies would not become disentangled until April 9, 1865, when Lee surrendered and his men went home.

The most successful and feared Confederate commerce raider of the war, the CSS Alabama, sinks after a spectacular battle off the coast of France with the USS Kearsarge.

On June 22, 1864, Union forces attempt to capture a railroad that had been supplying Petersburg, Virginia, from the south, and extend their lines to the Appomattox River. In the Battle of Jerusalem Plank Road, the Confederates thwarted the attempt, and the two sides settled into trenches for a nine-month siege.

On June 25, 1864, four years into the Civil War, Pennsylvania troops for the Union, begin digging a tunnel toward the Rebels at Petersburg, Virginia, in order to blow a hole in the Confederate lines and break the stalemate.

On June 27, 1864, Colorado Governor John Evans issues a proclamation warning that all peaceful Native Americans in the region must report to the or risk being attacked, creating the conditions that will lead to the Sand Creek Massacre.

In the one-day Battle of Atlanta, the largest battle of the Atlanta Campaign, Confederate General John Bell Hood continues to try to drive General William T. Sherman from the outskirts of the city when he attacks the Yankees on Bald Hill. The attack failed, and Sherman tightened his hold on Atlanta.

On July 30, 1864, at the Battle of the Crater, the Union’s ingenious attempt to break the Confederate lines at Petersburg, Virginia, by blowing up a tunnel that had been dug under the Rebel trenches fails. Although the explosion created a gap in the Confederate defenses, a poorly planned Yankee attack wasted the effort and the result was an eight-month continuation of the siege.

On August 5, 1864, at the Battle of Mobile Bay, Union Admiral David Farragut leads his flotilla through the Confederate defenses at Mobile, Alabama, to seal one of the last major Southern ports. The fall of Mobile Bay was a huge blow to the Confederacy, and the victory was the first in a series of Yankee successes that helped secure the re-election of Abraham Lincoln later that year.

On August 6, 1864, Union General Ulysses S. Grant meets with General Philip Sheridan at Monocacy Junction, Maryland, to give him his orders for his new role as commander of the Army of the Shenandoah. Those orders read, in part: "In pushing up the Shenandoah Valley...it is desirable that nothing should be left to invite the enemy to return. Take all provisions, forage and stock wanted for the use of your command; such as cannot be consumed, destroy."

Confederate General Jubal Early pulls out of Winchester, Virginia, as Union General Philip Sheridan approaches the city. Wary of his new foe, Early moved away to avoid an immediate conflict.

The Geneva Convention of 1864 for the Amelioration of the Condition of the Wounded and Sick of Armies in the Field is adopted by 12 nations meeting in Geneva. The agreement, advocated by Swiss humanitarian Jean-Henri Dunant, called for nonpartisan care to the sick and wounded in times of war and provided for the neutrality of medical personnel. It also proposed the use of an international emblem to mark medical personnel and supplies. In honor of Dunant’s nationality, a red cross on a white background—the Swiss flag in reverse—was chosen. The organization became known as the International Committee of the Red Cross. In 1901, Dunant was awarded the first Nobel Peace Prize.

On September 1, 1864, as Union Army General William Tecumseh Sherman tightened the noose on Atlanta, Georgia, shelling civilians and cutting off supply lines, General John Bell Hood commanded his Confederates forces to retreat. Atlanta, the Confederacy's second-most important hub after the capital Richmond, surrendered to Union forces the next day. Sherman had been strategically moving to capture the city since May.

In preparation for his march to the sea, Union General William T. Sherman orders residents of Atlanta, Georgia, to evacuate the city.

Confederate spy Rose O’Neal Greenhow drowns off the North Carolina coast when a Yankee craft runs her ship aground. She was returning from a trip to England.

A Confederate attempt to regain ground that had been lost around Richmond, Virginia, is thwarted when Union troops turn back General Robert E. Lee’s assault at Darbytown Road.

Union General Philip Sheridan averts a near disaster in the Shenandoah Valley when he rallies his troops after a surprise attack by Confederate General Jubal Early and scores a major victory that almost destroys Early’s army at the Battle of Cedar Creek in Virginia.

On October 26, 1864, the notorious Confederate guerrilla leader William “Bloody Bill” Anderson is killed in Missouri in a Union ambush.

On October 30, 1864, the town of Helena, Montana, is founded by four gold miners who struck it rich at the appropriately named “Last Chance Gulch.”

On October 31, 1864, anxious to have support of the Republican-dominated Nevada Territory for President Abraham Lincoln’s reelection, the U.S. Congress quickly admits Nevada as the 36th state in the Union.

On November 8, 1864, Northern voters overwhelmingly endorse the leadership and policies of President Abraham Lincoln when they elect him to a second term. With his re-election, any hope for a negotiated settlement with the Confederacy vanished.

On November 11, 1864, on orders from Union General William T. Sherman, Union soldiers begin destroying all railroads, factories and commercial buildings in Atlanta, Georgia—anything that could help support the Confederacy's military or economic goals. (Historical records cite the destruction starting anywhere from November 10 to November 12.) The actions dealt a crippling blow to the Confederacy during the Civil War, just days before Sherman began his scorched-earth March to the Sea.

On November 15, 1864, Union General William T. Sherman begins his expedition across Georgia by torching the industrial section of Atlanta and pulling away from his supply lines. For the next six weeks, Sherman’s army destroyed most of the state during his so-called March to the Sea before capturing the Confederate seaport of Savannah, Georgia.

Legend holds that on November 21, 1864, President Abraham Lincoln composes a letter to Lydia Bixby, a widow and mother of five men who had been killed in the Civil War. A copy of the letter was then published in the Boston Evening Transcript on November 25 and signed “Abraham Lincoln.” The original letter has never been found.

On November 26, 1864, Oxford mathematician Charles Lutwidge Dodgson sends a handwritten manuscript called Alice’s Adventures Under Ground to 12-year-old Alice Liddell.

On November 29, 1864, peaceful band of Southern Cheyenne and Arapahoe Native Americans are massacred by Colonel John Chivington’s Colorado volunteers at Sand Creek, Colorado.

On November 30, 1864, the once proud Confederate Army of Tennessee suffers a devastating defeat after its commander, General John Bell Hood, orders a frontal assault on strong Union positions around Franklin, Tennessee. The loss cost Hood six of his finest generals and nearly a third of his force.

On December 22, 1864, Union General William T. Sherman presents the city of Savannah, Georgia, to President Abraham Lincoln. Sherman captured the city after his famous March to the Sea from Atlanta. Savannah had been one of the last major ports that remained open to the Confederates.