Henry worked for his father at the Souther Tide Mills and prior to the arrival of the railroad, had been doing a good business. Extensive amounts of grain were brought to the mill by ship and cart and were processed to create a wide assortment of flours, meals and brans. Henry had bought out his junior partner, Micah Humphrey and was sole proprietor of the "old stand" Souther's Grain Store at the Washington and Coddington Street corner.

The Southers were well respected grain dealers in town. Extra shipments of grain were brought to the mill and store by schooner; up the Quincy Canal, from New York. Based upon the farming and stone-working economy, Quincy had a new stone "meeting house" and a new stone Town Hall, while John Souther, Sr., (Henry's father) served on the building committee of both Quincy Landmarks. The Souther Shipyard did a bustling business, launching schooners, brigs, stone sloops and an occasional full-rigged ship. A saw mill near the grist mill cut logs into plank and boards.

Industry and prosperity halted abruptly, however, in December 1846. Shortly before Christmas that year, Henry Souther got news that both the tidal grist mill and the tidal saw mill were destroyed by fire. An unidentified "incendiary"; possibly a new urban drunk and disorderly, torched both buildings in the night and the valuable complex, with contents, was proved to be a near total loss come morning. Henry had been insured adequately for his customers' lost grain, but he had inadequate coverage to replace the wood industrial buildings.

The townspeople of Quincy made donations and Henry sold his "carry-all" (a form of horse-drawn wagon) and rented rooms to raise additional funds. The project to rebuild the grist mill was further supported by the fact that the fire had not burned the whole mill priviledge entirely. The dam, stone wharves, first floor framing and some of the first floor planking survived intact.

Henry Souther had little choice but to rebuild. He was a family man with a wife and many children to feed. Within a season or two, Henry had succeeded in rebuilding the Souther Grist Mill, essentially as it exists today. However, the pre-1846 tidal saw mill, on the other side of the wharf from the grist mill, was not rebuilt until some thirty years later, by John Lincoln Souther, Henry's older brother.

According to the 3 Nov 1849 Quincy Patriot, Henry and his younger brother, Edward, and his son, Henry, Jr., departed Boston on the ship "Richmond" and headed west during the "Gold Rush" period. The ship "Argonaut" left the same day. Upon his return in the mid 1850's, he quit the grist mill business to go into the brewery business with his brother-in-law, James Phipps. Henry also owned the Bass Rocks Hotel. The 1867 Boston City Directory shows his business name to be Henry Souther & Company, (with Harrison Phipps Souther and William Felt Tufts, his son and son-in-law). He later removed to South Boston.

Henry also served as Broadway National Bank president from Nov 1861 to Jan 1876. [Bio courtesy of Richard Dennis Souther, Souther Family Association historian, 28 August 2010]