[1] He began working as a marble and wood carver, and then gained entrance to the McMicken School of Design in Cincinnati.

The effect of the German study was that he retained much of the Neo-Classical flavor in his art while most other sculptors of his generation were drawn towards Beaux-Arts realism.

By virtue of being a native Ohioan, he was commissioned to sculpt two statues of the recently assassinated President James Garfield; one for Cincinnati (Garfield's home city), and the other, in another pose, for the National Statuary Hall Collection at the United States Capitol.

In later years, he was to place statues of Oliver P. Morton of Indiana (1900), John J. Ingalls of Kansas (1905), Zachariah Chandler of Michigan (1913), George W. Glick of Kansas (1914), Ephraim McDowell of Kentucky (1929), and Henry Clay of Kentucky (1929) in the collection.

[5] Niehaus had eight statues in the National Statuary Hall Collection at the United States Capitol in Washington, D.C., a record for a sculptor.