The Hartnett Realty Company was founded by Mrs. Catherine Forbes Hartnett on October 20, 1947. The original office was located at 94 Broad Street in downtown Charleston, South Carolina. During its first year of operation, the company handled nine residential sales and returned a small profit. Mrs. Hartnett, one of the first women Realtors in Charleston, also founded the Women's Council of Realtors in Charleston and served as Chairman of the South Carolina Real Estate Commission prior to her death in 1978.

Since its inception, The Hartnett Realty Company has moved four times, always within downtown Charleston, as the business has grown. The first relocation was to 95 Broad Street; subsequently, the company moved to 272 Meeting Street, 7 and 9 Cordes Street, and most recently to 134 Meeting Street, where the business is currently based.

The Hartnett Realty Company added property management and insurance to its core business, real estate sales, in 1948, the same year that Thomas C. Hartnett joined his wife in the firm. By 1955, the company had over 250 properties in its management portfolio.

Thomas Forbes Hartnett enlisted in his parents' business in 1961 and by 1965, had launched the company into the real estate appraisal business. During the period that Mr. Hartnett served in the U.S. Congress, 1980 to 1986, the company sold the property management and insurance businesses.

Today, under the leadership of Thomas F. Hartnett, the company continues as one of the oldest real estate firms in South Carolina and the oldest real estate appraisal firm in Charleston.

The Hartnett Realty Company is a full-service real estate firm, offering maturity as well as experience in sales, appraisal, property management and consulting.