05May1864:  The hand-to-hand fighting was atrocious during the Battles of Wilderness and Spotsylvania, including a particularly devastating fire that swept through Saunders Field.

 Before the fire. however, both sides stopped to observe and cheer a Confederate and Yankee that had gotten into an old fashioned  fistfight after discovering the other in a gully in which both had sought refuge.  Both removed hats and coats and proceeded to duke it out.  It was reported that the Confederate won the fistfight, taking his captive back into the gully, as a signal for the vicious fighting to commence.
 
MORE:  http://www.nps.gov/history/history/online_books/civil_war_series/25/sec3.htm#3 

Allegheny (Pittsburgh) Arsenal Explosion
Seventy-eight young women were killed in the worst civilian disaster of the Civil War on Sept. 17, 1862.

These women assembled paper cartridges from paper, highly explosive black powder, and lead bullets.

MORE:  http://civilwarwomenblog.com/allegheny-arsenal-explosion (by Maggie MacLean, 03Apr2014)

April 3-4 1864; The Battle of Elkin’s Ferry, Okolona, Arkansas occurs. During the Union’s Camden Expedition, the Confederates fail to prevent Union forces from crossing the Little Missouri River.

April 8th 1864; The Battle of Mansfield/ Pleasant Grove/ Sabine Crossroads, Louisiana. When Gen. U.S. Grant took command of the Union Armies in early 1864, he makes plans for several offensive actions. He decided to embark on a campaign up the Red River. He envisions a combined effort with army, navy moving up the Red River with troops on gunboat. The Union forces are moving too slowly and the Confederates set a trap and defeat the Union forces at Mansfield south of Shreveport. Union forces fail to support the original plan and retreats back to New Orleans. During the retreat the flotilla is stranded by a falling river level at Alexandria. It takes nearly 3,000 soldiers, sailors and marines to free the strand boats and allows then to escape. The red River campaign ends in a complete failure.

April 9th 1864; The Battle of Pleasant Hill, Louisiana occurs. Union forces retreating after the Mansfield defeat are rallied and turned to face a major Confederate attack. Both sides lose over 1,500 troops.

Also in 1864 

• The Union army begins to replace the single shot rifled musket with the Spencer repeating rifle. This breech loading rifle holds 6-8 round before it has to be reloaded.
• Casualties from Juniata County, Pennsylvania. Pvt. Conrad Lingle, 53rd  PVI, Company “I”, from the Richfield area, dies on April 6th 1864, from wounds received near Spottsylvania, Virginia. 
• Pvt. John McNew; 47th Company “C”, of Mifflintown, is wounded at Pleasant Hill, Louisiana, April 4th 1864…  Pvt. Robert Rodger; 138th Company “H” of Walker Township, is wounded at Wilderness, Virginia, April 6th 1864… Pvt. Thomas Nipple; 47th PVI Company “C” of Milford Township, is wounded at Sabine Cross Roads, Louisiana, April 8th 1864…Pvt. James Kennedy; 161st Company “F” of East Waterford is wounded at Pleasant Hill, Louisiana, April 9th 1864… Pvt. Benjamin Wall; 47th PVI Company “C”, of Lack Township, is wounded at Pleasant Hill, Louisiana…

Contribution by Pen Teller