What significant action did Rene-Robert Cavelier de La Salle take in 1685?

Rene-Robert Cavelier de La Salle's significant action in 1685 involved the unintentional arrival of approximately 400 settlers at Matagorda Bay. This event was pivotal as it marked an attempt to assert French claims to the territory around the Mississippi River and its vicinity, although the venture faced many challenges. La Salle's expedition was meant to establish a French presence in the region, yet it ended up in a situation where the large group of settlers found themselves in a difficult position due to various factors such as navigation errors and miscalculations.

Understanding this context provides insight into the impact of La Salle's actions and the historical significance of the expedition for both French colonial ambitions and the subsequent interactions with Indigenous populations and other European powers in the area. The other options represent notable historical activities, but they do not encapsulate the specifics of La Salle’s unexpected arrival in Matagorda Bay with a large group of settlers, which was a defining moment in that expedition.