(The name is spelled many ways, it is also seen as: Ohlhausen, Olhausen, Ohlhaussen, Ahlhausen, Aalhausen, Aalhaus, Ohlhaeusser, and even Woolheiser.)
Ohlhaüser is the spelling of the name of our immigrant Ohlheiser ancestors as it was recorded for their births and Baptisms in the church registers of the Catholic Church in Spechbach, Baden-Würtenburg, Germany. Other members (some certainly and others almost certainly) of the same family had life events recorded in the churches, Catholic and Protestant, of nearby villages with considerable variations of the spelling as noted above.
Our Ohlheiser lineage can be traced, with reasonable certaintly, only to Joseph Ohlhaüser (c.1757-1830), in Spechbach, Margraviate of Baden (now Baden-Württemburg, Germany)... he was the father of the immigrant, Johan Joseph, who arrived in this country in 1846 with his family (and styled himself "Joseph Ohlheiser"). There are other Ohlhaüsers named in the Church records at Spechbach but, while they are undoubtedly part of our family, their relationship has yet to be established.
The Ohlheisers are among the most recent of our immigrant ancestors. But the earliest of any of our Immigrant Ancestors are also to be found in this Ohlhaüser/Ohlheiser line by way of Joseph Ohlheiser's (the younger's) marriage to Hattie S. Darling. Hattie's ancestors can be followed back to their immigration in 1620 (and to even much earlier dates, well beyond the time-frame of this family history/genealogy). It's a long story best followed through the genealogy pages of this site. A good place to start the story might be with Claire Maxine Ohlheiser, our most recent Ohlheiser grandmother.