Final answer:
The Springer Amendment opened the Oklahoma District and unassigned lands for settlement, which aligns with option 'A'. It did not establish a territorial government.
Step-by-step explanation:
The Springer Amendment refers to an amendment that was passed to open the Oklahoma District and unassigned lands. This allowed for non-Native American settlements on a first-come basis and it declared April 22, 1889, as the official day for settlers to enter parts of what would become the state of Oklahoma and stake their land claims. The amendment did not create a territorial government, which is related to the provisions of the Land Ordinance of 1787. Therefore, the correct answer to what the Springer Amendment did is that it opened the Oklahoma District and unassigned lands, which is option 'A'.