As often as possible, he found his way to go into less physical and and better paying jobs. Several years moved to a small town just north of today's Bardstown. It was there in Fairfield, Kentucky in 1855 that he opened a flour mill. Henry bought a plot of land at the edge of town, built a grain elevator and mill, and set about grinding wheat into flour for their neighbors.  In those days the gristing process yielded a great deal waste.  Because he had so much waste and nothing of consequence to do with Henry bought a farm and fed the waste to farm animals like pigs. But he had too much waste from the mill that he had to find find something to do with the rest, so he decided to turn the rest into wheat whiskey. McKenna set up a wooden still in the back of his flour mill and began turning out about a barrel of whiskey a day. At first he used only wheat to make wheat whiskey but eventually turned to the most prevalent and affordable grain in the Commonwealth in corn to make his whiskey.  With corn and a charred oak barrel McKenna experimented and learned the art of making true bourbon.  A newspaper account of the day stated that McKenna, his son and a slave distilled a "an over abundant amount of good whiskey quality for the still he had." By 1858 Henry had enough business to hire a full-time distillery superintendent, he hand picked Patrick Sweeney who like Mckenna and his wife Lizzie was another Irish immigrant from County Derry. By 1870 Henry at the age of 51 was still living in Nelson County with Lizzie, four boys, Daniel, 21; John, 20; James, 15; Stafford, 7, and a girl, Mary who was 11. His occupation was given in the U. S. Census as “distiller and miller.” Note the distiller came first. As his grew up he had enough income to provide them all good private educations. He also enlisted all four boys at an early age to learn and help him in his distilling business.

McKenna is said to have been a stickler for sanitation.  He never simply whitewashed his fermenting tubs with lime as most of the early distillers did to save time. Henry had them scrubbed with soap the sterilized with boiling hot water before reusing.  According to McKenna this, "was the only way to insure that 'wild' yeasts did not adulterate his new batch".  The Louisville Courier of the time also credited him as "unique among Kentucky distillers for refusing to sell his whiskey until it had been aged at least five years."
In 1880 McKenna opened a business office on Louisville’s Market Street to sell his whiskey to a broader audience. Unfortunately he rapidly outgrew that facility and had to invest in other property.  He bought “The Old Blue House” on Market Street, which was a famous landmark at the time. That name of that house was one of three images etched in blue on McKenna’s Whiskey Ceramic Jugs. To meet the production demand for his "fine whiskey" he again had to move his Louisville distillery and corporate offices. This time he chose Fourth Street and Main, soon to be identified as Louisville’s “Whiskey Row” because of the number of distillers that set up shop there.

Because of the over abundance of care McKenna took to make his whiskey, it very popular and in high demand.  In 1883 he built a brand new brick distillery on "Whiskey Row and it had the capacity to make three barrels a day, seven days a week.  Testimonials published in the newspaper from recognized figures helded sales contiue to grow. A local doctor in Louisville Dudley Reynolds was quoted saying:  “Henry McKenna’s whiskey is the purest and best I have ever seen.”  By the 1890s the Irishman’s "Old Line Sour Mash Whiskey" was being sold throughout the continental United States.  

Over time McKenna became widely recognized as one of the true patriarchs of Kentucky whiskey.  In 1892 Congress introduced a bill asking for a five year bonding time for bourbon whiskey.  Although it not pass that year the bill was known as “The McKenna Bill.”  Just under a year later in 1893, McKenna passed away at age 75.  He was buried in Saint Michael’s Cemetery in Fairfield, Nelson County. 

McKenna who sent his two eldest sons to universities for advanced educations asked them to carry on the family business of distilling after he passed. Daniel McKenna, his oldest, took over the management of the distillery. He was perfect for the job since he was had worked in the business from about age six. His brother, James McKenna, was also intricately involved in the family business. He headed up the marketing and distribution of the family’s whiskey from his Louisville office.

By today’s standards, the McKenna production was very small.  Family members have insisted that capacity never exceeded more than nine barrels a day and then only for nine months of the year. You see, Henry believed that summertime was bad for correct fermentation of the mash, he insisted that production be ceased for three months each year.