Between 1820 and 1930 approximately 4.5 million Irish immigrants came to America. The story of why they left is fairly well known, many fled the potato famine and religious discrimination, or sought employment or a better life than they could achieve at home. Their numbers however were dwarfed by the number of Germans who came to America during the same period (roughly 7.5 million between 1820 and 1880 alone). The story of German emigration is less well known. Were there single issues akin to the potato famine which caused large numbers to leave? Did people from particular regions/countries of Germany form a majority and was there a majority of Catholics or Protestants among emigrants. Finally did the rise of the German Empire in 1870 stem the flow of people departing?
The story of German immigration is not that different than any other country's immigration story. 1815 formed the German Confederation. Comparing Germany to other countries at the time - Britain, France - it lacked industrialization. Germany still had many of the older ways and was an agrarian society. It was a new country with its own struggles. 1815 also marked the end of the Napoleonic Wars and it left Germany's economy in ruins. Between economic ruin and a food shortage in Germany in the first half of the 19th Century, it led to the first major wave of German immigration of the Century.
Germany suffered many years of bad harvests so there were people who were hungry. Hunger riots occured and those who did not own a farm, like artisans, were among the first major group to immigrate. Widespread famine and increased prices of potatoes and grain led to many people looking to immigrate, especially by the 1840's.
The 1830's brought about a major population increase in the countryside. Farmer families were having many children. Land was scarce and there was the risk of losing the land was very real for farmers and their families. Loss of land meant losing once's source of life. Thus many farmers immigrated to the Midwestern United States where plenty of land was avaliable.
Immigration was also advertised in Germany. Family that immigrated earlier wrote back to family telling them about the great new life they had. Those letters were published in German newspapers. America also advertised cheap and plentiful land which attracted many German immigrants.
The year 1848 also marked the second wave of German immigration. The second wave consisted of professionals such as professors, politicians, and journalists. The first wave was mostly farmers and those who worked in a trade. In Europe as a whole, 1848 was a year full of revolution, and Germany was no exception. People wanted liberal reform. The 1848 revolution in Germany led to a desire of a German state and a constitution. People wanted better living conditions.
Those who left were people in positions of power who were targeted by the lower and middle classes rebelling for a better life. This group had money and was able to immigrate easier than the first group. This group became known as the 48ers, because of the time the immigrated.
The final group was the 1870s and 1880s. Germany itself at this point was starting to industrialize a lot. The prominent group of immigrants this time around were Volga Germans, who were Germans that settled in Russia. These people were also farmers that owned a lot of land. Tsarist Russia took all that land away. These farmers immigrated to America for the same promise of the first group: cheap and plentiful land.
The US was considered the most powerful country in the world by this time and attracted many immigrants. There was a lot of opportunity for work whether it was owning land on a farm or working in factories. The American Dream led many to leave their home country to come to America for a better life.
In terms of religion, it was fairly split. Protestants were mostly from North Germany and Catholics were Southern Germany. One notable group though was German Jewish immigrants. German-Jewish immigrants formed their own small communities and had their own reformed synogogues and all. The Protestant and Catholic Germans both went to the midwest for farming and land owning opportuinies mostly.
By the 1870's, German immigration slowed the down. Life was better in Germany by 1870 between an increase of industrialization, German unification, and better opportunity. There was an economic downturn in the 1870s and 1880s which led to another wave of immigration. Prussia was the region mostly impacted this time around since it was home to many farmers who faced economic hardship. Industrial Germany was taking off again by the late 1880s and relatively unaffected by immigration this time around.
The next time Germany had an increase immigration to the US was around the World Wars. However the US also enforced stricter immigration rules by then, limiting how many immigrants could enter from each country each year.
Sources: Irish and German Immigrants of the Nineteenth Century: Hardships, Improvements, and Successes by Amanda A. Tagore (2014)