Censusrecords.com allows customers to search all available US census records. Brightsolid said it was the first site to do this in the US market.
The online publishing and technology group, owned by DC Thomson, runs several UK genealogy sites.
It also owns friends reunited.co.uk, which it bought from ITV in March 2010 for £25m.'Fresh choice'
The new US site will house the 1940 US census records when they are released later this year - which Brightsolid said was one of the most "eagerly anticipated" developments in family history research in recent years.
Chris van der Kuyl, chief executive officer of Brightsolid, said: "The launch of censusrecords.com is just our first offering to the US market. It will be followed later this year by the launch of findmypast.com, which will be our flagship American brand.
"We know that there is a global demand in family history for the sort of accurate data, innovative search and customer focus that we are known for providing.
"We are excited about the big year we have ahead of us as we look to provide fresh choice and value to Americans interested in researching their ancestry."
Brightsolid operates findmypast.co.uk, genesreunited.co.uk and scotlandspeople.gov.uk. It launched Irish and Australian versions of findmypast.co.uk last year.
The company is also collaborating with the British Library to digitise 40 million newspaper pages over the next 10 years.