Hallo D As fare as I know are the dates (by Laura Crow) about Peter & Ursula Saxer-Mengelt (which emigrated with 9 children about 1855 from Switzerland to the USA) correct.
About 1845 emigrated Anton & Ursula Saxer-Mengelt with two children to USA. The relationship between these two Saxer families remains for me an open question. In the 19th century "Ursula" was a very frequent first name at Spluegen, and there were different lines of Saxer and Mengelt families.
If you'd like more information about Spluegen and the Mengelt families don't hesitate to ask or to visit the Mengelt Web Sites .