The brief answer to your query is that Wilson's ultimate fate not only remains unknown, but that even his motives for refusing Jackson's pardon – the sole reason, now, that he is remembered at all – remain obscure. The longer version is that it is possible to at least sketch in some background to the case; that the version of events that appeared in the National Gazette seems likely to be at least mostly correct; and that we can be practically certain that he was not hanged.

Let's begin this tale at the beginning. Wilson was a native of Trenton, N.J., who was born c.1806. A newspaper account originating in the Philadelphia Bulletin, which was published after his conviction, suggests he had a difficult childhood; the family was poor, and his father, who was a watchman and then a sailor, is supposed to have left him "a stranger to that paternal oversight which should have directed his youthful footsteps in the path of rectitude. " He received an at best limited education, learned no trade, and "while still very young" committed an unspecified "larceny" that saw him sentenced to two years in jail.

Putting together a rough timeline of Wilson's life, it seems likely that this first crime was committed while Wilson was still aged about 16. He served two years for it in Walnut Street Prison, Philadelphia, where he attracted the attention of the superintendent, S.R. Wood. Wood attempted to reform him, and, on his release, arranged for him to take an apprenticeship in Delaware. Wilson apparently remained there for two years, and "a thorough reformation had apparently taken place" when, by a piece of terrible bad luck, his master took on another employee who had known Wilson in Philadelphia. This man broke the news that he was a convicted felon, and the boy was expelled from his position, a blow "so tremendous... as almost to deaden his faculties." His hopes "irretrievably blasted", he felt, he drifted into casual farm labour in New Jersey, where "the virtuous impressions left upon his mind gradually faded away." He committed another larceny in Maryland, served several years hard labour for the offence, and, while in prison there, made the acquaintance of two other crooks, James Porter and Abraham Poteet, with whom he planned to embark on a new career as highway robbers.

We have a couple of takes on what happened next. According to Wilson, he was an at best reluctant accomplice in the mail coach robberies that actually went down, being "overawed by the threats of the others, who forced him to become a partner in their scheme of plunder." Porter, on the other hand, seems to have denied this and sought to lay the majority of the blame on Wilson. Whatever the truth, the trio's first robbery yielded $830 and emboldened them to stage a second heist. On the night of 26 November 1829, they attacked the mail coach that ran from Philadelphia to Reading, which turned out to contain cash to the value of $8,200. The sum this time was large enough to result in a large-scale man-hunt, and, as a result, "each one became suddenly apprehensive that the others had betrayed him," and "mutual confessions followed."

Highway robbery with menaces was then an offence punishable by death in Pennsylvania and, while no one had actually been physically harmed in the Reading Mail robbery, at least one of the men confessed that had been willing to use lethal violence if there had been "the least resistance," an admission that led to a charge of "putting the life of the driver [one Samuel McCrea] in jeopardy". Poteet was designated a mere accomplice, but both Porter, who was aged about 35, and Wilson – who was by then aged 24, but looked much younger – received death sentences from Justice Henry Baldwin, a Philadelphia circuit judge who also served on the Supreme Court at a time time when service on the latter court remained a part-time job. The sentence on Porter, who seems to have been generally considered both the ringleader and the more violent of the pair, was actually carried out at the end of June 1830. By this time Wilson had withdrawn his not guilty pleas, and had pleaded guilty to all the indictments against him,

One unfortunate feature of the case as reported in the case law summaries that remain by far the most accessible sources for the Wilson case is that these exhibit almost no interest in either Wilson himself, or in the precise details of what happened next; only the peculiarity that the pardon he received from President Jackson was, somehow, refused is of any interest them, and we learn essentially nothing about either the reasons why the pardon was granted, or the reasons why Wilson refused it. Luckily, however, a stray newspaper account in a Virginia paper, published in August 1830, casts some light on this not insignificant part of the story. It seems that, to begin with, public sentiment in Pennsylvania then ran against the imposition of the death penalty in cases such as this, and that a substantial number of people protested Wilson's sentence on the grounds that "the youth of the prisoner, the full, candid, and effective confession which he made at an early moment" and the "meekness" of his conduct while in prison awaiting execution alike urged mercy.

As a result, a "distinguished minister of the Gospel" (unnamed) intervened by writing directly to Jackson, who put in motion an investigation that satisfied him not only that Wilson was genuinely penitent, but also that none of the Reading Mail robbers would have been convicted had it not been for the full confession that he had offered; that the information that Wilson had supplied (also unspecified) had prevented at least two further mail coach robberies; and that he had "under all circumstances... abstained from the shedding of human blood." Jackson thus issued a pardon, dated 14 June 1830. This pardon covered the capital part of the crime, but not some of the subsidiary charges, and so Wilson knew at the time he refused the offer that he would remain incarcerated in full expectation that "the remnant of his days will... be passed in prison at hard labor."

No contemporary source that I have been able to locate covers Wilson's refusal of the pardon, much less the reasons why he turned it down, and the next we hear of him is in 1841, when several newspapers report that President Van Buren issued a further pardon to him. None of these papers state why that pardon was issued, what exactly it covered, or even whether it was actually accepted.

All I can add to this sad tale is that the ESPY File, an all-but-complete record of every execution carried out in the United States, lists five capital sentences carried out on men named George Wilson, but three of those men were Black, one was convicted of espionage in 1862, and the last, a man of unknown ethnicity who actually was hanged for robbery, was not executed until 1896. We can therefore be pretty certain that the Smithsonian was in error in stating that our Wilson was hanged, and I suspect it may have confused him with his accomplice Porter, who was executed.

This investigation leaves us with plenty of unknowns. Wilson appeared in court at the time that the pardon was issued, and averred that "he had nothing to say, and that he did not wish in any manner to avail himself, in order to avoid sentence in this particular case, of the pardon referred to." I can find no record that he ever explained himself in this respect, and the view of the Supreme Court was pretty gnomic, too: its sole comment was that "it is hardly necessary to speculate on the case of a man refusing to accept a pardon in a capital case." If I was to speculate in its place, I would say it might be just possible that Wilson refused the Jackson pardon because he so regretted his involvement in the stagecoach robbery; some of the contemporary press coverage certainly accepted that he felt genuine contrition for the crime. More likely, however, the refusal was a product of the confusing nature of the charges brought against him; the Supreme Court spent quite a bit of time trying to work out how precisely Jackson's pardon applied to each of the multiple charges that he faced, and it may be that the refusal was part of some legal strategy related to this.