After 1839, Shaw sold his hardware business and retired from an active life in business. A fellow St. Louis businessman who knew Shaw personally wrote the following account of the events that led up to Shaw’s decision to retire.
When the balance sheet for 1839 was struck it showed, to the great surprise of Mr. Shaw, a net gain for the year of over $22,000. He could not believe his own figures, and so went over them again and again until he could no longer doubt the fact. Telling the story many years afterward he said it seemed to him then that "this was more money than any man in my circumstances ought to make in a single year," and he resolved then and there to go out of active business at the first good opportunity. The opportunity presented itself very early in the following year, and was promptly improved by the sale of his entire stock of merchandise. So at nearly forty years of age - only the noon of life - with all his physical and mental powers unimpaired and vigorous, Henry Shaw was a free man - and the possessor of $250,000 with which to enjoy that freedom. There is every reason to believe that, with his exceptional qualifications for success in this department, he might easily have increased the $250,000 to $2,500,000 long before he had reached the age of sixty. By 1840, the population of the city was on the cusp of an extended period of population growth brought about by the influx of German and later Irish immigrants who began to settle in the northern and southern portions of the city. Within a period of a few short years the population of the city would begin to grow yearly by the thousands and it became clear that real estate would prove a lucrative endeavor of which Shaw would partake in during his remaining years. Shaw retired, not because he was afraid of losing what he had made, or thought he could not make any more; but because he felt he had enough, and intended to enjoy it. He always owned his money; his money never owned him. His tastes and habits were simple and sensible; he lived well but not extravagantly, and with not the slightest attempt at ostentation. Up to the last years of his life, be drove himself in the one-horse barouche which was his sole equipage, and not until friends warned him of the dangers incident to growing infirmity did he indulge in a carriage and coachman.
As mentioned above, Shaw retained the attitudes and habits of an English gentleman for his entire life. In the 19th century, an English gentleman’s education was not considered complete until he had made the "Grand Tour," an extended trip through Europe. Such extended travels were considered necessary to expose the gentleman to the arts, languages and cultures of the great civilizations of Europe. After his retirement, Shaw took advantage of his newly found free time to make just such a Grand Tour of Europe. Leaving his sister, Caroline Shaw, in charge of his interests in St. Louis, Henry Shaw made several extended stays in Europe over the next decade, staying on the Continent for up to three years at a time.
In 1851, Shaw made his final trip abroad in order to attend the first World’s Fair in London. On this trip, he visited the Royal Botanic Gardens at Kew and the Crystal Palace Exhibition. He also saw the wonderful gardens at Chatsworth, the Duke of Devonshire's country seat in Derbyshire. These gardens were two of the finest gardens in the world, and they inspired Shaw. It was apparently during his walk through Chatsworth Gardens that Shaw conceived of the idea of creating his own garden on his properties in St. Louis. For the rest of the life, the creation and care of a garden and a park on his property would be his principle occupation.