Leon Dyer was born on 2 Oct 1807 in Mayene, Germany and was the son of John Maximilian and Babette (Nachmann) Dyer. Leon's birth name was Feist Emanuel Heim/Haim.

In about 1812, the family immigrated to the United States and first settled in Baltimore, MD and began a meat packing business.

Leon's siblings: Rosanna Dyer Osterman (Mrs. Joseph) , Isadore Dyer , Hannah Dyer Symonds (Mrs. Henry D.) , Joseph Dyer, Barney Dyer and Abraham Dyer .

On 4 Oct 1833, Leon took the Oath of Citizenship of the United States of America in the District Court of the United States in the Maryland District in Baltimore, MD. In the court order, he states he renounces his allegiance to the "Empire of Germany."

Dyer participated in the Second Seminole War and was with General Winfield Scott in Florida when they engaged the Seminole Indians, who had massacred 110 U.S. Army soldiers in December 1835.

On 28 February 1836 in New Orleans, LA, Dyer was appointed a the Regimental Quartermaster of the Regiment of Louisiana Volunteers by the Governor of Louisiana, Edward D. White, Sr.

In April 1836, Dyer met General Thomas Jefferson Green in New Orleans, LA and joined the Texas War of Independence. With a company of 29 men command by Captain William Graham from New Orleans, Dyer embarked on the Schooner Sarah Carter, bound for Galveston, arriving on 20 April 1836, two days after the Battle of San Jacinto. On 18 May 1836, he received a commission as Major in the Texas forces, signed by the President David G. Burnett, the first President of the Republic of Texas. He was appointed as an aid-de-camp to General Green. The Louisiana contingent was assigned to the force of General Green, and saw active service clearing western Texas of bands of plundering Mexican troops.

Prior to leaving New Orleans for service in the Army of the Republic of Texas, Dyer became involved in a dispute with a Mr. Smith of New York wherein a challenged was issued. Due to his leaving for Texas, Dyer could not attend to the duel but in leaving, he promised Smith a meeting upon his return. In November 1836, Dyer returned to New Orleans, aboard the Schooner Fanning, because rumors had begun that "Old Baltimore had backed out." Upon Dyer's arrival from Texas, William Graham informed Smith that the parties would meet at 7 a.m. on Sunday morning. Dyer was first on the ground and was accompanied by his second and Dr. Jones. Upon Smith's arrival, pistols were loaded, 10 paces measured and the parties having taken a stand, fired and the results were neither ball took effect. Dyer attempted to reload, but his second stated to that, "honor had been satisfied." And that was the end of the duel.

In January 1837, Dyer was assigned the task of escorting General Santa Anna to Washington, DC. It was during this trip that Dyer approached other family members about coming to Texas.

During the Mexican War (1846-48), Dyer is supposed to have joined the U.S. Army, to again serve with General Scott, as a Colonel and Quartermaster.

In 1848, Colonel Dyer crossed the plains to California where he settled in San Francisco and founded a Jewish Congregation. In 1849, he organized the first Jewish Congregation on the Pacific Coast and served as President of that new congregation until late 1850. In September 1849, he attended the Rosh Hashanah service, which, are considered the first public Jewish religious observance in the Far West at the tent store of Lewis Franklin on Jackson Street in San Francisco, CA. Again in September 1850, Dyer stepped up and raised $500 to rent the Masonic Hall in San Francisco, so the members of the Kearney Street Congregation could observe the High Holidays. At the end of the High Holidays, Dyer led the Simchat Torah service and afterward hosted an elaborate dinner at Philip Mann's Boarding House.

On 18 Nov 1850, Dyer left Havana, Cuba for New York aboard the United States Mail Steamship Company's the SS Ohio, a wooden-side-wheeled-steamer. On 23 November 1850, the ship arrived in New York. By 29 November 1850, Dyer is in Columbus, OH, where he is thanked in an article in the Daily Ohio Statesman newspaper for providing copies of recent newspapers he brought with him from San Francisco, Panama, Havana and New York.

In 1852, President Millard Fillmore enlisted Dyer to deliver confidential dispatches to the Prussian government in Berlin. Dyer was commended for this mission.

In ca. 1852, probably in Germany, Leon married his first cousin, Sarah Nachman, who was the daughter of his mother's twin brother, Joseph Nachman. They are known to have the following children: John Maximilian Dyer , Dr. Joseph Osterman Dyer , Isabella Dyer and Dr. Alexander "Alex" Abraham Dyer.

Major Leon Dyer died of dysentery on 14 September 1883 in Louisville, Jefferson Co., KY. His body was shipped to Galveston, Galveston Co., TX for burial. The funeral was conducted at 4 p.m. on 9 October 1883 from the home of his brother, Isadore. Burial was in the Hebrew Benevolent Society Cemetery.

Later, the family had a lovely mausoleum built over the family graves.