A past search on the website of Ellis Island shows that from the time they started keeping records in 1892, a total of 96 people with the last name of Japp arrived in America through Ellis Island. My ancestor arrived before that, so I'm sure that several others also arrived before 1892. I'll be happy to start a new line of ancestors, just send in your Japp genealogy information.
More branches of Japp families can be added to this site. Simply email in your Japp genealogy information starting with the oldest known Japp ancestor and their dates of birth, death, marriage, and location. I have seen Japp families listed on the internet in the USA, Britian, Germany, Canada, Scotland, and Australia.