Helen Fiske was born in Amherst, Massachusetts, a daughter of Nathan Welby Fiske and Deborah Waterman Vinal. She had two brothers, both of whom died after birth, and a sister named Anne. Her father was a minister, author, and professor of Latin, Greek, and philosophy at Amherst College.

Fiske was orphaned at a relatively young age. Her mother died in 1844 when she was fourteen, and her father died three years later in 1847, when she was seventeen. Her father had provided for Helen to be cared for by an aunt. Before he died, he had ensured her education. Helen Fiske attended Ipswich Female Seminary and the Abbott Institute, a boarding school run by Reverend J.S.C. Abbott in New York City. She was a classmate of the poet Emily Dickinson, also from Amherst. The two corresponded for the rest of their lives, but few of their letters have survived.

In 1852 at age 22, Helen Fiske married United States Army Captain Edward Bissell Hunt. They had two sons. Murray Hunt died as an infant in 1854 of a brain disease. Her husband died in a military accident in 1863. The second son, Rennie Hunt, died of diphtheria in 1865. At age 35, Helen Hunt was widowed and childless.

In 1875, she remarried to William Sharpless Jackson, a wealthy banker and railroad executive. They had met while visiting at Colorado Springs, Colorado, at the resort of Seven Falls.

Jackson began writing after suffering the deaths of her family members. She published her first work anonymously.

She also traveled a great deal. In the winter of 1873-1874 she was in Colorado Springs, Colorado, in search of a cure for tuberculosis. Over the next two years, she published three novels in the anonymous No Name Series, including Mercy Philbrick's Choice and Hetty's Strange History.

Jackson was moved by the issues of Native American, as she learned about government defaulting on treaties, the Indian Wars, and removal of Indians to reservations. She wrote the book, A Century of Dishonor (1882), about US government treatment of Native Americans.

Becoming involved as an activist, Jackson wrote numerous articles for newspapers and magazines. She was appointed an agent of the Bureau of Indian Affairs to collect information and make recommendations to improve the lives of Mission Indians in Southern California, who had been mostly dispossessed of former lands. After sending her 56-page report to the Bureau, she was pleased to learn of legislation incorporating many of her recommendations. It passed the Senate but died in the House.

Determined to capture people's hearts to force change, she wrote the novel, Ramona (1884), dramatizing the ill treatment of Indians in Southern California. It gained quick and broad success after its publication, but people responded to it mostly as a romance novel.

Jackson died of stomach cancer in 1885.

Scholars refer to her as Helen Hunt Jackson. She did not use that name, but went by her married names: Helen Hunt and Helen Jackson.

In 1879 her interests turned to the Native Americans after hearing a lecture in Boston by Ponca Chief Standing Bear. He described the forcible removal of the Ponca from their Nebraska reservation. Upset by learning about the mistreatment of Native Americans by government agents, Jackson became an activist. She started investigating and publicizing government misconduct, circulating petitions, raising money, and writing letters to The New York Times on behalf of the Ponca.

A fiery and prolific writer, Jackson engaged in heated exchanges with federal officials over the injustices committed against Indians. Among her special targets was U.S. Secretary of Interior Carl Schurz, whom she once called "an adroit liar." She exposed the government's violation of Indian treaties. She documented the corruption of Indian agents, military officers, and settlers, who encroached on and stole Indian lands.

She won the support of several newspaper editors who published her reports. Among her correspondents were editor Willliam Hayes Ward of the New York Independent, Richard Watson Guilder of the Century Magazine, and publisher Whitelaw Reid of the New York Daily Tribune.

Jackson also wrote a book summarizing and condemning state and federal Indian policy, as well as the history of broken treaties. Because she was in poor health, she wrote with haste. A Century of Dishonor, calling for significant reform to government policy towards Native Americans, was published in 1882. Jackson sent a copy to every member of Congress with an admonishment printed in red on the cover, "Look upon your hands: they are stained with the blood of your relations." To her disappointment, the book had little impact on government policies and actions.

Jackson went to southern California for respite. Having been interested in the area's missions and the Mission Indians on an earlier visit, she began an in-depth study. While in Los Angeles, she met Don Antonio Coronel. The former mayor of the city, he had also served as State Treasurer. A well-known authority on early Californio life in the area, he had served as the former inspector of missions for the Mexican government.

Coronel told her about the plight of the Mission Indians after 1833. They were buffeted by secularization policies of the Mexican government, as well as later US policies, both of which led to their dispersal from mission lands. Under its original land grants, the Mexican government provided for resident Indians to be allowed to continue to occupy lands. After taking control of the territory, the US generally disregarded such occupancy claims. In 1852, there were an estimated 15,000 Mission Indians in Southern California. By the time of Jackson's visit, they numbered fewer than 4,000 people.

Coronel's account inspired Jackson to action. She was noted by the U.S. Commissioner of Indian Affairs, Hiram Price, who recommended she be appointed an Interior Department agent. Jackson's assignment was to visit the Mission Indians, ascertain the location and condition of various bands, and determine what lands, if any, should be purchased for their use. With the help of Indian agent Abbot Kinney, Jackson traveled around Southern California and documented conditions. At one point, she hired a law firm to protect the rights of a family of Saboba Indians facing dispossession from their land at the foot of the San Jacinto Mountains.

In 1883, Jackson completed her 56-page report. In it, she recommended extensive government relief for the Mission Indians, a program including the purchase of new lands for reservations and the establishment of more Indian schools. A bill embodying her recommendations passed the U.S. Senate but died in the House of Representatives.

Jackson refused to be discouraged by the Congressional rejection. She decided to write a novel to depict the Indian experience "in a way to move people's hearts." She was inspired by Uncle Tom's Cabin, written years earlier by her friend Harriet Beecher Stowe. "If I can do one-hundredth part for the Indian that Mrs. Stowe did for the Negro, I will be thankful," she told a friend.

Although Jackson started an outline in California, she began writing the novel in December 1883 in her New York hotel room, and completed it in about three months. Originally titled In The Name of the Law, she renamed it Ramona (1884). It featured a part-Indian orphan raised in Spanish Californio society and her Indian husband, Alessandro, based on some of the people she knew and incidents she had encountered. The book achieved rapid success among a wide public.

Encouraged by the popularity of her book, Jackson planned to write a children's story about Indian issues. But, less than a year after the publication of Ramona, she died of cancer in San Francisco, California.

Her last letter was written to President Grover Cleveland; she urged him to read her earlier work A Century of Dishonor. Speaking to a friend, Jackson said, "My Century of Dishonor and Ramona are the only things I have done of which I am glad. They will live and bear fruit."

Biographer Valerie Sherer Mathes writes:

"Ramona may not have been another Uncle Tom's Cabin, but it served, along with Jackson's writings on the Mission Indians of California, as a catalyst for other reformers .... Helen Hunt Jackson cared deeply for the Indians of California. She cared enough to undermine her health while devoting the last few years of her life to bettering their lives. Her enduring writings, therefore, provided a legacy to other reformers, who cherished her work enough to carry on her struggle and at least try to improve the lives of America's first inhabitants."

Jackson's A Century of Dishonor is still in print, as is a collection of her poetry.

The public has responded to the novel more as a romantic love story than as a tract of political reform. Having had many editions, Ramona is still in print. The novel of Ramona was adapted as a play and for three films. Each year, the city of Hemet, California stages The Ramona Pageant, an outdoor play based on Jackson's novel.

The films featured Mary Pickford in Rosita (1923), Dolores del Río in Ramona (1928), and Loretta Young in Ramona) (1936). Young was partnered by Don Ameche.

• Her grave is in Evergreen Cemetery, Colorado Springs, Colorado

• The Helen Hunt Jackson Branch is a Mission/Spanish Revival style building built in 1925 as a branch of the Los Angeles Public Library; it is listed on the National Register of Historic Places.

• The largest collection of the papers of Helen Hunt Jackson is held at Colorado College.

• A high school in Hemet, California, and an elementary school in Temecula were named after her.

• Helen Hunt Falls, located below Seven Falls, was named in her memory.

• Bits of Travel at Home (1878)

• Bits about Home Matters (1873)
• Saxe Holm's Stories (1874)
• Mercy Philbrick's Choice (1876)
• Ramona (1884)
• Between Whiles (1888)
• A Calendar of Sonnets (1891)
• Ryan Thomas (1892)