His daguerreotype self-portrait taken in 1839 is generally accepted as the first known photographic portrait of a person taken in the United States, and a significant achievement for self-portraiture.

He operated some of the earliest photography studios in the United States between 1840 and 1842 and implemented innovative techniques to significantly reduce the exposure time required for portraits.

He created and patented the "solar lamp" in 1843 which burned brighter and allowed for the use of cheaper lard as a fuel source rather than more expensive whale oil.

In late September 1839, soon after the daguerreotype was publicized, Joseph Saxton took a picture of the Philadelphia Central High School, which is considered one of the oldest photographs taken in the United States.

Sachse began interviewing Cornelius and other members of the American Philosophical Society in order to record the history of photography in the United States.

[6] Working alongside chemist Paul Beck Goddard, Cornelius made significant advancements in reducing exposure times for daguerreotypes.

Through the use of bromine, better plates and the implementation of reflectors and blue glass filters to enhance lighting conditions, they managed to decrease the exposure time for daguerreotype portraits to less than a minute.

[7] As the popularity of photography grew and more photographers opened studios, Cornelius either lost interest or realized that he could make more money at the family gas and lighting company.

Cornelius revised a British lamp design which forced additional air into the burner and allowed for the burning of lard rather than whale oil.