To my knowledge, there were two Walkenhorst lines that migrated to the U.S.- one to the Cincinnati area and one to the Missouri area. I believe they are from the same general area in modern Germany. When they left it was Prussia and I think each family came from places near Hannover, perhaps Werther and Melle.
The first Walkenhorsts in the Cincinnati line migrated to the United States in approximately 1854. They came from Bremen to Baltimore, then to Cincinnati. Bremen was the closest departure point from the Hannover area.
Perhaps someone in your family will know approximately what year the first person in your family came to the United States and from where?
That might be helpful in establishing a link between the two lines.