One important thing to keep in mind when researching ancestry is that present-day Poland's borders do not match up with the historic Polish borders. As a part of the complicated process of redrawing the map of Europe at the tail end of the Second World War, the Allies shifted Poland's borders westwards while the USSR assumed control of its eastern portions. These new Polish areas in Silesia were very much ethnically German and many of these Germans were expelled to make room for displaced Polish settlers. So, for example, if your grandfather's birth certificate leads you to present-day Wrocław, odds are that he was a German citizen and ethnically German as Breslau (the German name for Wrocław) was predominantly German city in the Silesia.

As for the status of Poland in the nineteenth century, it is complicated. The Congress of Vienna redistributed the partitioned Poland yet again, with Austria receiving Polish Galicia, Prussia the region around Posen- shaded red, and Russia receiving the lion's share of Polish territory in an entity known as either Congress Poland or the Kingdom of Poland. While each of these Polish territories were nominally autonomous states governed through a personal union with the Habsburgs, Hohenzollerns, and Romanovs respectively, in practice this autonomy was largely fictive. Each of the governing states sought to defang Polish nationalism and enacted various discriminatory measures against Polish national activism.

Russia imposed the most extreme repression of the three. After a series of national uprisings in 1829 and 1863, Russia abolished Congress Poland and replaced it with a series of gubernias (as a side note, a Jewish ancestry webpage has an awesome map and description of these administrative changes, entities governed by a governor-general appointed by St. Petersburg. Ethnic Poles were forbidden to enter into the gubernias's government and Polish education and printing was severely restricted. In geographic areas the Russian state deemed naturally Russian such as regions of present-day Belarus, the state actively closed down Catholic churches, forbid the Polish language, and enacted various Russification policies to reclaim the land for Russia. Anti-Polish rhetoric became a staple of the emerging Great Russian nationalist movement. Poles in these gubernias were subjects of the tsar, not citizens, and subject to increasing state restrictions and surveillance.

In the Grand Duchy of Posen, the Prussian and later Imperial German authorities implemented a series of Germanizing initiatives to transform the region's inhabitants into Germans. The anti-Catholic repression of the Kulturkampf, which began in the 1870s, never really abated in Posen. The German state forbid the teaching of Polish and these harsh educational measures erupted into a series of mass civil protests in 1901 over the teaching of German. Yet, unlike Russian Poland, German Poles enjoyed the rights of citizenship, including male suffrage, and legal protections. Although the German state officials were heavily anti-Polish and sought to undermine these legal restrictions, Posen became one of the electoral strongholds for the Catholic Centre Party.

Austrian Galicia was the most leniently governed of the partitions. Like Russia, Poles in this area were subjects and not citizens, but the Habsburgs governed through a local diet elected through a highly restrictive franchise based upon income. Galicia itself was the poorest region of the empire and this political arrangement heightened class tensions. When Polish aristocrats sought to rally the Polish peasantry against the Habsburgs in 1848, the peasants famously chopped the heads of the noblemen and presented them to the Habsburg authorities. By the late nineteenth century, Polish nationalism in Galicia sought to work within the existing political framework of the Austro-Hungarian Empire to pry more political concessions with an eye towards autonomy. However, Vienna was never really willing to grant this level of autonomy and was predisposed to be inimically hostile to nay expression of irridentist nationalism. Despite this unsatisfying political stasis, Austro-Poland relations were much more quiet than their two northern neighbors in the nineteenth century.

Finally, it should also be underscored that just because an individual was born in a geographical space called Poland, it does not follow that they would automatically consider themselves Polish. National identity was constantly in flux in this period and not an automatic given. Many individuals were bilingual and their self-identification could change dependent upon the larger situation. And the experience of being ruled by a foreign empire does have an impact upon culture. For example, because the Russian state forbid them from serving in Poland, many educated Poles entered into the Russian bureaucracy serving in the hinterlands of Russian Central Asia, where they discovered amidst a predominantly Muslim population that they were culturally more Russian than Pole.

During the tail end of the 18th century, the Commonwealth of Poland-Lithuania was ineffective and sickly, being a minor regional power compared to the more famous Prussia to it's West and the large Russia in the East. As a result, Frederick the Great and Catherine the Great decided to nibble away at Poland-Lithuania, which would end up being the first of three Partitions of Poland, with Austria joining in the End. With a minor exception during the First French Empire (1806-1813), Poland was occupied and split between these three powers until the end of World War I.

This map will show you roughly how Poland was divided. Part of Poland (such as the southern part where Krakow is) was a part of the Austro-Hungarian Empire, the larger part to the East was owned by the Russian Empire which held Warsaw, and to the West the German Empire owned Silesia and northern Poland. Depending on where she was born, he'd belong to one of those three empires.