[4] The Fisher–Miller Land Grant set aside three million acres (12,000 km2) to settle 600 families and single men of German, Dutch, Swiss, Danish, Swedish, and Norwegian ancestry in Texas.

[3] Prince Carl of Solms-Braunfels secured the title to 1,265 acres (5.12 km2) of the Veramendi grant the next year, including the Comal Springs and River, for the Adelsverein.

With no food or shelters, living in holes dug into the ground, an estimated 50% die from disease or starvation.

About 200 German colonists, who walked from Indianola, founded the town of New Braunfels at the crossing of the San Antonio-Nacodoches Road on the Guadalupe River.

About 150 settlers petitioned the Texas Legislature to establish a new county, suggested names "Pierdenales" or "Germania".

The melee apparently started when County Clerk John M. Hunter, who also owned the store, refused to sell whiskey to a soldier.

[17][18] John O. Meusebach was elected to the Texas Senate in 1851 to represent Bexar, Comal, and Medina Counties,[9] and in 1854, received a special appointment as commissioner from Governor Elisha M. Pease to issue land certificates to those immigrants of 1845 and 1846 who had been promised them by the Adelsverein.

[21][22] Surveyor Jacob Kuechler was commissioned as a captain by Sam Houston to enroll state militia troops in Gillespie County.

Texas seceded from the Union in 1861, and joined the Confederate States of America, and Houston was dismissed from office in March by the Confederacy.

Unionists from Kerr, Gillespie, and Kendall Counties participated in the formation of the Union League, a secret organization to support President Abraham Lincoln's policies.

The Union League formed companies to protect the frontier against Indians and their families against local Confederate forces.

[25][26] Spring Creek Cemetery near Harper in Gillespie County has a singular grave with the names Sebird Henderson, Hiram Nelson, Gus Tegener, and Frank Scott.

The inscription reads “Hanged and thrown in Spring Creek by Col. James Duff’s Confederate Regiment.” [27][28] Kiowa raiders massacred residents of the McDonald farm in the Harper vicinity in 1864.

[29] During 1865, Gillespie County suffered a war-time crime wave, as 17 individuals were convicted of murder.

[35] Chester W. Nimitz, future Commander in Chief, United States Pacific Fleet, was born in 1885 in Fredericksburg.

His father, Chester B. Nimitz, died before his birth, leaving his seaman grandfather as role model.

[9] In 1908, future President of the United States Lyndon B. Johnson was born in a small farmhouse on the Pedernales River.

[39] In 1948, the county began its annual Easter Fire event to commemorate the Meusebach treaty signing.

[41] The Japanese Garden of Peace, a gift from the people of Japan, was dedicated on the 130th anniversary of the founding of Fredericksburg at the Nimitz Museum on May 8, 1976.

That same year, it is also added to the National Register of Historic Places,[43] The Texas White House officially opened to the public August 27, 2008.

While Texas was overwhelmingly Democratic up until recent decades, Gillespie County has long been a Republican stronghold.

This is largely due to the heavily German American heritage of the county and that Gillespie was the fountainhead of Texas’ small Unionist movement during the Civil War.

Most Texas Germans acquiesced to secession, but Fredericksburg was still self-sufficient and sold surplus food to the army.

School districts in the county include:[58] It is within Central Texas College's attendance area.