Beginning with about 1870 (post-Reconstruction), how did the status of women, Native Americans, and African Americans each change from the late nineteenth-century to the twenty-first-century? What were the major events and forces (including key individuals) that affected each in that time period, and what are the greatest triumphs and challenges of each? What are the current struggles each is facing today?

Women and African Americans in the United States have historically had to struggle to obtain the same rights as white males, and it’s true that history books tend to focus on "dead white guys." The common denominator between the evolution of women’s rights and African American’s rights from the nineteenth to twenty-first-century is largely based upon reaching towards some semblance of equality.
Women in the early twentieth-century, for example, were fighting for the right to vote, and—consequently—the Women's Suffrage Movement paved the way for the fight for other rights. Suffrage was granted in 1920 with the Nineteenth Amendment. As women became more educated, they began to question supposed normalcy of their role (or lack of it) in education and politics. In the 1960s, the women's rights movement pushed the boundaries of this "normalcy." The iconic “housewife” role was combatted heavily by the sheer empowerment of women at the time. In the words of Carrie Chapman Catt, president of the National American Woman Suffrage Association, "No written law has ever been more binding than unwritten custom supported by popular opinion." That is to say harmful stereotypes of what a "good woman should be" needed to be shattered in order to obtain equality. This sentiment encapsulates the women's rights movement through modern times, as gender bias still continues to affect women's roles in the workplace, politics, and healthcare, in terms of representation, wages, pregnancy discrimination, and access to affordable birth control, to name a few.
Similarly, the civil rights movement fought to seek equality for African Americans since the abolition of slavery (Thirteenth Amendment) in 1865. Shortly after, in 1870, African American men were granted the right to vote with the Fifteenth Amendment. Following Reconstruction, the notion of "separate but equal" was challenged, much like the stereotypical roles of women. Growing educational opportunities paved the way for much of the progress made in the twentieth-century, as many African Americans looked to role models such as Booker T. Washington for inspiration. In Up From Slavery, Washington says,

Among a large class, there seemed to be a dependence upon the government for every conceivable thing. The members of this class had little ambition to create a position for themselves, but wanted the federal officials to create one for them,

expressing a similar sentiment to Chapman Catt, that one must fight for rights beyond the mere constraints of the law. Indeed, in modern times, African Americans are still fighting to combat harmful stereotypes which affect their roles in politics, the workplace, healthcare, and relations with law enforcement—again, to name a few.
This is, truthfully, only the tip of the iceberg—so to speak—but many parallels can be drawn between the struggles faced by women and many ethnic minorities in the history of the United States. And, oftentimes, the mass feelings of empowerment from one success pave the way to a new fight, bringing these groups one step closer to equality.