Final answer:
The European powers involved in the ownership of St. Louis in the 1800s were Spain, France, and the United States. St. Louis was initially under Spanish control, transferred to France, and later became part of the United States through the Louisiana Purchase.
Step-by-step explanation:
The European powers involved in the ownership of St. Louis in the 1800s were Spain, France, and the United States. Initially, the area was controlled by Spain until the early 1800s. However, in 1801, Spain ceded Louisiana, including St. Louis, to France. The United States subsequently purchased the Louisiana Territory from France in 1803, known as the Louisiana Purchase, which included the important trade center of St. Louis.