In 1983, President Ronald Reagan proclaimed October 6 as German-American Day to celebrate and honor the 300th anniversary of German American immigration and culture to the United States. On August 6, 1987, Congress approved S.J. Resolution 108, designating October 6, 1987, as German-American Day. It became Public Law 100-104 when President Reagan signed it on August 18. A proclamation (#5719) to this effect was issued October 2, 1987, by President Reagan in a formal ceremony in the White House Rose Garden, at which time the President called on Americans to observe the Day with appropriate ceremonies and activities.
German-American Day is a holiday in the United States, observed annually on October 6. The holiday, which celebrates German American heritage, commemorates the date in 1683 when 13 German families from Krefeld, near the Rhine, landed in Philadelphia. These families subsequently founded Germantown, Pennsylvania, the first German settlement in the original thirteen American colonies, and organized the first petition in the English colonies to abolish slavery in 1688. Originally known under the rubric of "German Day", the holiday was celebrated for the first time in Philadelphia in 1883, on the occasion of the 200th anniversary of the arrival of the settlers from Krefeld; and similar celebrations developed later in other parts of the country.
Source: wikipedia.org