I don't know specifically which short stories Charles Eastman first published. More research into his body of work is needed.
Since we don't have enough information given here, it's impossible to name the short stories that Charles Eastman first published. However, his works generally revolved around Native American themes such as the relationship between Native Americans and the encroaching white society, their traditions, and their ways of life. To find out about his first published short stories, it would be advisable to look into his early works, perhaps starting with the first anthologies or collections of his writings.
We are not informed about the particular short stories that Charles Eastman first published. His writing was important for representing Native American voices and cultures. To determine the first short stories he published, one might explore bibliographies of his works, read critical analyses of his literary career, or search for early reviews of his writing which could potentially mention the initial short stories that he put out.