He graduated with honours from the College of the City of New York in 1864 with a Bachelor of Science and Master of Arts, and subsequently went to study at the Universities of Heidelberg and of Paris.
In 1873 he married Bianca Saroni, the daughter of one of his patients, in Boston, and the following year they moved to San Francisco, where Herz was appointed a member of the Board of Health.
In September 1877, along with George Prescott, Thomas Edison signed an agreement with Stephen Field and Cornelius Herz regarding European Quadruplex telegraph patents.
Herz was the originator and principal founder of the Society for Working the State Telephonic-Telegraphic Trunk Lines, with a capital of 100,000,000 francs, a gigantic scheme to interconnect the 36,000 communes of France by a perpetual day and night uninterrupted telephonic-telegraphic service, and to connect villages and the smallest hamlets at a uniform rate (names and addresses free) of one half-penny per word.
U.S. President James Garfield appointed Dr. Herz an official representative of the United States Government to the International Congress of Electricians in Paris in 1881, and that same year he was raised to the rank of Commander of the Legion of Honour.
It was common knowledge in Paris that Baron Reinach and Dr. Herz had been associated together during a dozen years and more in vast commercial undertakings, involving financial transactions amounting to many millions.
The pursuit of Dr. Herz was aided by the greed of some persons in the camp of the Reinachs, who sought to acquire fortune through the downfall of a man whom they now were only too willing to consider an adversary, by taking advantage of the tragic circumstances attending the Baron's death and of the confusion in which he had left his affairs.
Georges Clemenceau's political judgment was called into question by his flirtation with the demagogic General Boulanger and by his friendship with the "crooked financier" Cornelius Herz, who was heavily implicated in the Panama scandal.
In order to stop his counsel from producing his proofs of Baron de Reinach's debt to Herz (consisting of documents on stamped paper duly dated and signed by the Baron, and held by the Rothschilds in their bank) the presiding Judge took advantage of the technicality that the documents were insufficiently stamped, a pure oversight doubtless on the part of men of business, and required that a fine amounting to about L 50,000 sterling should be paid before their introduction as evidence be admitted.
It is also a fact that during the very time the French were persecuting Dr. Herz, by processes in the Civil and Criminal Courts in Paris, by utilizing the Extradition Treaty with England, and by public vilification through the Parisian Press – who accused him of being a traitor, a spy in the pay of England, an incendiary, a murderer, and guilty of a whole host of minor crimes – prominent members of the various Governmental and Opposition groups were constantly giving assurances to Madame Herz, and friends of the doctor, as well as to his legal representatives, that all would soon be “set right.”[citation needed] After keeping Herz under wrongful arrest for three and a half years, the French government withdrew their charges and said they had made a mistake.