I was following this discussion on the Hassinger list.

Other census records seem to confirm Germany as the birthplace of John D Hassinger.

1870 New York City, 20th Ward - J D Hassinger, born in Hesse Darmstadt, age 46 - wagonmaker. Margret, born in Baden, age 38.

1860 New York City, 20th Ward - John Hessinger, born in Hesse, age 36, blacksmith. Margt, born in Hesse, age 28.

I wasn't able to locate this family in the 1880 census records