According to a family monument in Laurel Hill Cemetery in Philadelphia, Thomas Leiper was born in Strathven (sic) on 15 December 1745. The date of birth cited identifies him as that son of Thomas Leiper, Innkeeper at Strathaven in Lanarkshire, who baptism was registered at Avondale on the same date, although this important fact is not mentioned in his Wikipedia Biography.
https://en.wikipedia.org/wiki/Thomas_Leiper
The monument was evidently raised by his descendants (in or later than 1882), although, currently, his profile overview does not explain what it was that led them to believe that he was born in Strathaven on 15 December 1745. Did they commission research in Scotland, or was his date and place of birth recorded on one of his papers in the United States, or in a family Bible, perhaps?
Help in identifying surviving record evidence from the USA would be welcomed.