The information came from census records. There are very few you can find online without paying a fee. You might try the library in your area. Here's something you might keep in mind while looking for your ancestors:
Wuerttemberg, Germany Emigration Index Johannes Landmesser & wife Catharina (March 1852). Both were born in Muenchingen
A Johannes Landmesser md Eleonore Seifert 8/1/1853 NY,NY - 1st German Presbytarian Church. His bd is listed as 12/5/1830 and hers 1/9/1831
I did look in the census in 1850 in Ny & NJ but did not find them. The spelling of the name is probably the biggest problem.