The poem "Still I Rise" by Maya Angelou is spoken by a first person narrator who is not explicitly named in the poem. The poem is in the shape of a speech by the narrator to an also unnamed "you."
Both the diction of the poem and contextual information about its author and when it was written suggest that the "I" is intended to be a black woman. The references to a slave past suggest that the poem is about African-American descendants of slaves, rising up from a history of oppression in the United States. The "nights of terror and fear" suggest lynch mobs. Many of the dialectical features of the poem also suggest African-American English.
There are several ways the poet indicates gender. The term "sassiness" is one applied almost exclusively to women. The images of the speaker dancing and having diamonds between her thighs also suggests a black woman rising above sexual and racial oppression.
The reason for the speaker not being fully individuated is that the poet probably intends the "I" to represent a potentially universal experience of black women rather than the particular experience of some individual black woman.