Like many things in this poem, who the speaker is isn't exactly clear. Don't pull your hair out trying to pin it down (it's not a good look for anyone—ask Miley Cyrus). The identity of the speaker isn't really what's important here. Dove wants us to focus on the subject—Rosa Parks—much more than the speaker. Whoever the speaker is, it seems like there is some time between that day in 1955 and this poem, and even though the title of the poem seems pretty familiar and cozy, it doesn't seem like the speaker knows Parks personally.
There is a tone of reflection, of looking back into the past and gazing through a camera lens with historical perspective. The reflective tone is best captured in the first line, and line 10, which begins the final stanza: "How she sat there" and "How she stood up." That "how" is super-important. It's totally different from "that." The speaker isn't observing the fact that Parks did these things but how she did them.
Right away in the first stanza, you get the sense of historical reflection with lines 2 and 3: "the time right inside a place / so wrong it was ready." Without some hindsight, it would be pretty tough to make that statement. This speaker is in the present, right alongside us. Luckily we get to look over his (or her—it's never made clear) shoulder through that special Rosa Parks camera lens (not available for sale) that helps capture her so perfectly.