Unmarried and working as a barrel organ player. Living in Stockholm, Sweden. [Source: Swedish Census 1900]
He did not have a son by name Andrew Watson, living in New Orleans in 1900. The Peter Costa who was living with his wife Antonia in New Orleans at the time of the US census 1900 was a different person, but possibly this profile could be adapted to represent Peter Costa. Pietro Costa did not have much of a connection to Sweden.
↑ "United States Census, 1900." Database with images. FamilySearch. http://FamilySearch.org : 14 June 2016. Citing NARA microfilm publication T623. Washington, D.C.: National Archives and Records Administration, n.d.