Links to related sites and useful resources . . . 
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The Battle of the Rosebud
Rosebud Battlefield State Park — official site
Rosebud Battlefield — a short-lived (2012-2013), but fascinating and informative blog by historical archaeologist Chris Merritt, "dedicated to the history and archaeology of the Rosebud Battle of June 17, 1876, known to Native American tribes as "Where the Girl Saved Her Brother."
Wooden Leg's Account of the Battle of the Rosebud (excerpted from Wooden Leg: A Warrior Who Fought Custer, by Thomas B. Marquis, 1931.
"Rosebud Gets No Respect: A Nearly Forgotten Battle is Overshadowed by its More Glorified Successor" — an article by Daniel Brown in True West magazine. 
Rosebud Battle Lost in the Little Bighorn Story, by Mary Pickett, Billings Gazette (by way of the Rapid City Journal). 
A Young Mother at the Rosebud and Little Bighorn Battles (Women's History Matters blog). 

The Battle of the Little Bighorn
Little Bighorn Battlefield National Monument -- official National Park Service site. 
Little Bighorn Battlefield National Monument -- Digital Archive on NPGallery
Little Bighorn National Monument official park map (300KB pdf)
Friends of the Little Bighorn Battlefield — this non-profit, official partner organization raising funds and provides volunteers to to aid and support management programs and objectives at the national monument. Bob Reece's website is a treasure trove of fascinating reading, resources, and photos. While you're there, don't forget to join the "Friends." 
National Park Service Historical Handbook to the Battle of the Little Bighorn, by Robert Utley (Washington, DC, 1969
The Battle of Little Bighorn: An Eyewitness Account by the Lakota Chief Red Horse recorded in pictographs and text at the Cheyenne River Reservation, 1881 (from PBS: New Perspectives on the West)
Battle of the Little Bighorn, from Encyclopedia of the Great Plains, entry by Douglas Scott
The Battle of the Little Bighorn, by Nathaniel Philbrick, article from American Heritage. 
Plains Indian Ledger Art - Department of Ethnic Studies UCSD
Different View of 'Custer's Last Stand' in Red Horse's Battle Drawings - KQED article on Stanford exhibit
Archeology at the Battle of the Little Bighorn — a tremendously useful summary of the work done at the battlefield in the 1980s and '90s, with a detailed bibliography for anyone interested in a "deep dive" into the subject. 
The Reno Court of Inquiry: The official record of a court of inquiry convened at Chicago, Illinois, January 13, 1879, by the President of the United States upon the request of Major Marcus A. Reno, 7th U.S. Cavalry, to investigate his conduct at the Battle of the Little Big Horn, June 25-26, 1876 (University of Wisconsin Digital Collection)
Reno's official report.
General Terry's telegram reporting on the Battle of the Little Bighorn

The Battle of Antietam
Antietam National Battlefield -- official National Park Service site.
Auto Tour Map — Area Map for Directions — Monument Locator Map
Save Historic Antietam Foundation — Established in 1986, SHAF is working to promote the preservation and restoration of the scenic area in and around the Antietam Battlefield.
Antietam on the Web: Your reference to the 1862 battle at Sharpsburg, Maryland, a tipping point in the American Civil War
Antietam Resources from the American Battlefield Trust — Indispensable information, including maps and articles, from the premier American battlefield preservation organization. 

The Apache Wars
Our Culture -- Mescalero Apache Tribe
Historic Photos of the Apache, Edward R. Curtis Collection, Library of Congress
The Apache Wars: A Timeline, part one -- Birth of Mangas Coloradas
The Apache Wars: A Timeline, part two -- The Bascom Affair, Apache Pass, Apache Springs, Camp Grant
The Apache Wars: A Timeline, part three -- The Massacres Continue
The Apache Wars: A Timeline, part four -- From Lozen to General Crook
The Apache Wars: A Timeline, part five -- Geronimo Surrenders
The Apache Wars: A Timeline, part six -- Prisoners of War