Germany does not include a national index to their records. You need to know the town or city they lived and usually the parish they attended. Parish churches could cover serveral nearby towns. The parish where your ancestors’ records are located might be different from where they actually lived.
Also, shifting boundaries over the course of history affect your research as well. Poland/Germany and France/Germany boundaries shifted over time as an example.
These links may help in your research.
3 Essential Websites for German Family History Research -Legacy Tree
https://www.legacytree.com/blog/3-essential-websites-german-ancestors?…
Compgen.de – German Genealogy
http://compgen.de/
Landesarchiv – Baden-Württemberg
http://www.auswanderer-bw.de/sixcms/detail.php?template=a_artikel&id=6441&sprache=de
Bremen Passenger Lists
http://www.passagierlisten.de/
German Script Tutorial
https://script.byu.edu/Pages/German/en/welcome.aspx
German Marylanders
http://www.germanmarylanders.org/genealogy
Many Roads – German Immigrants 1850’s to 1890’s
http://www.many-roads.com/2015/03/22/german-immigrants-1850s-through-1890s/
Open Library – A collection of over thirty thousand names of German, Swiss, Dutch, French and other immigrants in Pennsylvania from 1727-1776
https://openlibrary.org/works/OL906306W/A_collection_of_up
wards_of_thirty_thousand_names_of_German_Swiss_Dutch_Fr
ench_and_other_immigrants_i
German Emigration Records
http://www.genealoger.com/german/ger_emigration_
records.htm
About Bremen in the world
http://www.die-maus-bremen.de/Datenbanken/auswanderer/index.php/?lang=de
Emigration from Southwest Germany (Click English on right toolbar)
http://www.auswanderer-bw.de/sixcms/detail.php?template=a_artikel&id=6591&
Bremen Passenger Lists (flag above right nav is option for English or Deutsch).
http://www.passagierlisten.de/
Archion
https://www.archion.de/
Archives Bas-Rhin France – Click on box I accept these conditions, then select one of the conditions. You can try both options to see what you like best. The second one is the one I used for finding my Untereiner family with the help of a Alsace-Lorraine Facebook member.
http://etat-civil.bas-rhin.fr/adeloch/index.php?refacces=
Archives Haut-Rhin France – I use google translate with this one.
http://www.archives.haut-rhin.fr/Services_Actes_Civils.aspx
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