well, let´s see...
After the kingdom of Prussia with help of their allied troops have won the franco-prussian war of 1870/71 they established a new gouvernement. Many little states teamed up together and formed the German Empire ( 1871 - 1918 ). http://en.wikipedia.org/wiki/German_Empire
The emperor of Germany was the king of Prussia.He ruled over all states in this foederation.
In the german - austro war (14 June – 23 August 1866) Austria lost the war and Germany annected the kingdom of Hannover. So the Us census 1870 states :Clara Angela was born in Kingdom Hannover. When she moved in 1865 it was the Kingdom of HANNOVER. After 1871 her birthplace was part of the state of Prussia.
Before 1871 the conditions for a move had been harder. They had been defined by law 07.April 1826 .
People had to prove that they had paied all debts and and that they own nobody any money. Male people needed a certificate of discharge from the army. 10 % of their propety they had to pay as a tax. They lose their citizen rights and were not allowed to move back.
When Johann August moved he definitly had to declare his intentions to the local court . So maybe at the state archive are records available.http://www.archive.nrw.de/lav/abteilungen/westfalen/oeffnung...
This archive is here in Münster
Clara Angela came 1865 . Probably with her father and 3 siblings on 05.Juni 1865.
Along came the Naturalization Act of June 18, 1798 - a time when political tensions were running high and there was an increased desire to guard the nation. The residence requirement for naturalization was raised from 5 years to 14 years.
Four years later, Congress passed the Naturalization Act of April 14, 1802, which reduced the residence period for naturalization from 14 years back to 5 years.
So when Johann August came in 1866 the earliest chance for naturalisation would be in 1871. Us census 1900 states he was naturalisized. According to your list he lived between 1870 & 1900 in Baltimore . So he should have been naturalisized there. For that they file two applications.
Maybe you have good luck here to track him back.