This miniature portrait is signed "Pollock, Balt." for Pollock of Baltimore.
Although he appears to be unrecorded as a miniature painter, it seems highly likely that the artist is the Henry Pollock of Baltimore who was a highly regarded daguerreotypist and photographer. He was born in 1810 and is listed in Baltimore city directories from 1849 to 1889. For more about him see Baltimore Daguerreans, K-R
As an indication of what a threat daguerreotypes were to miniature painters, Pollock claimed an output of 5,500 likenesses per annum. For an example of his work, see POLLOCK, HENRY,
The sitter is stated to be S S Wheeler and the portrait was probably painted around 1840-1850, although the frame dates from closer to 1830. 543