He was born in New York State, trained as a medical doctor and then enlisted in the army, later becoming a silver prospector.
In 1845 he went to Fort Leavenworth, Kansas where he enlisted in the US Army at the start of the Mexican American War and entered the service as a private even though he was a practicing physician in civilian life.
After he was discharged in early 1847, he resumed his quest for adventure, purchased a large ranch northeast of Los Angeles in the late 1840s, assisted some lost settlers who had mistakenly wandered through California's Death Valley, and opened a mining town in south central California.
In 1860, Darwin led another party into Death Valley in a second attempt to find silver, again without success.
The 1846 journey of General Stephen Kearny and his Army of the West across the wilderness of the southwestern United States has been the subject of many books and articles.
Dr. French was on that march and captured a vivid account of the Battle of San Pasqual, in which he fought.
Here they remained for a short time and then started for Santa Fe, N.M. On their way they met Gen. Kearny about 40 miles from the Rio Grande near headwaters of Gila diver.
Near Santa Fe they met Kit Carson who informed them that the trouble in Calif. was over and that the Mexicans were perfectly peaceable.
After marches long and arduous, almost famishing at times for water and very frequently short of rations, they came to the hills and mountains overlooking the valley of San Pasqual.
Here they camped near the residence of Mr. Stokes whither many of the officers retired to drink wine and have a good time generally.
commander, Andros Picho, ordered his men to “Come on and let us kill the d—d thieves.” The American troops were cold and wet; it having rained a little just before starting.
The next evening after the battle one man, Sergeant Cox, passed over the river to his long home.
thinking to intercept them in a narrow defile at the head of San Bernardo valley hastened whither.
French was one of Board of Supervisors when the court house was built, and in removing the records from Old Town to San Diego much trouble was experienced.
The above quoted account was written in Dr. French's hometown of Poway, California, a small town located north of San Diego.
In 1887, Dr. French was asked to provide his own eyewitness account of the final decisive battle for the future state of California in the Mexican–American War of 1846.
This account is a typewritten copy of a microfilm of the original dictation on file in the Bancroft Library at the University of California at Berkeley.