Thomas Jr. studied Ancient and modern languages and mathematics, but was also disciplined for disorderly conduct in 1825 and questioned in a gambling scandal the following year, which may have led him to enroll in a class in moral philosophy from prominent Virginia lawyer George Tucker.

[7] A Democrat, in 1833 and possibly through his father's connections, Swann secured an appointment from President Andrew Jackson as secretary of the United States Commission to Naples (Kingdom of the Two Sicilies - later Italy).

His bride's British born father, John Sherlock, left a sizeable estate which included interests in French and Neopolitan spoliation claims, as well as 6000 acres of Pennsylvania land, 150 ounces of silver plate, 300 bottles of madeira, plus stock in the Bank of the United States, three Baltimore banks, two turnpikes, a canal in York, Pennsylvania and the Baltimore and Ohio Railroad (which had been incorporated in 1827 and in completed track to Harper's Ferry by 1834).

Meanwhile, this Thomas Swann and his family lived on Franklin Street in Baltimore, and used his late father's Virginia property Morven Park as their summer retreat.

[13] In 1844 Swann became Alexandria' tobacco inspector,[14] an important responsibility in that port city which also had railroad ties both to Richmond, and (via a separate station) to Baltimore.

In 1846-1847, Swann was the B&O's lobbyist in Richmond, for the franchise the railroad had secured in 1827 was expiring, and its extension through western Virginia was opposed by the powerful political interests of the James River and Kanawha Canal Company.

[19] Additionally, Swann enacted a law that encouraged white fisherman to harass black fisherman when he signed into law the state's first ever "Oyster Code": "And be it acted, that all owners and masters of canoes, boats, or vessels licensed under this article, being White Men, are hereby constituted officers of this state for the purpose of arresting and taking before any judge or Justice of the Peace, any persons who may be engaged in violating any provisions of this article.

[25] In the 6th ward artillery was used, and a pitched battle fought on Orleans Street in East Baltimore/Jonestown/Old Town neighborhoods between "Know Nothings" and rival Democrats, raging for several hours.

[26] Swann's ally, Know-Nothing Congressman Henry Winter Davis, criticized Ligon's action both for subverting local authority and as an attempt to swing the election to the Democrats.

[18] Mayor Swann, this time running for re-election, successfully argued for a compromise measure involving special police forces to prevent disorder, and Steuart's militia were stood down.

Following the municipal purchase of the former private Baltimore Water Company, (since 1804), saw the replacement of its old wooden pipes and aging inadequate infrastructure with the beginnings of two water-sewage construction projects along the upper Jones Falls.

Following was the major public works project of the construction of the dam at the new Lake Roland Reservoir along with the organization of a new city water board and extension of new waterworks service into new outlying areas of the growing metropolis.

Ligon criticized Swann for not taking the necessary precautions, recalling the event as partisans "engaged; arms of all kinds were employed; and bloodshed, wounds, and death, stained the record of the day, and added another page of dishonor to the annals of the distracted city".

Swann was angered, and insisted this was not necessary, but, recalling the events one year earlier, Ligon refused to lift the martial law status.

In his inaugural address, he encouraged reunion in the State following the American Civil War, and voiced his opposition to slavery, deeming it "a stumbling block in the way of [our] advancement".

[citation needed] Radical Republicans of Maryland criticized Swann for supporting the Reconstruction policies of Democratic and 17th President Andrew Johnson, and refusing to adopt their proposals.

[28] Swann Park, off of South Hanover Street (Maryland Route 2) in the South Baltimore/Spring Gardens area, adjacent to the eastern waterfront of Middle Branch (Smith and Ridgley's Coves) of the Patapsco River is named for him and also serves as an occasional athletic home for the former Southern High School (now Digital Harbor High School).

In Virginia, both his childhood home, now called the "Swann-Daingerfield House"[29] and Morven Park still exist (although expanded by later owners) and have been listed on the National Register for Historic Places since the 1970s.