The papers of the Frans August Larson family span the years 1864-2021, with the bulk of the material dating from 1900 to 1980. The papers document the lives of a missionary family during their many years (1893-1939) in Mongolia and Kalgan (now known as Zhangjiakou), northern China, on the border of Mongolia, as well as their later lives in the United States. The papers are in English with occasional items in Swedish or Mongolian.

At the heart of the collection are the papers of Frans August Larson, Swedish-born missionary, expedition guide, entrepreneur, diplomatic advisor in Mongolia, and author of Larson, Duke of Mongolia. Larson's file includes drafts of his posthumously published memoir and of an unpublished book about Mongolia, both written in the 1940s. The largest correspondence file in the collection is his letters written to his daughter, Mary, beginning when she left China to attend high school in California and continuing until his final days when he was living in California and she in Connecticut. The letters document family life, missionary activities, life in Mongolia, social occasions with friends, his work with expeditions and business concerns, and world events as they unfolded in China and Mongolia and the part that he played. The majority of the letters to his daughter, however, were written during his later years while living in Alabama, California, and British Columbia, Canada. His file also includes material documenting his art collecting of Ordos bronzes and his work with art dealers. Additional material about Frans August Larson is found throughout the papers. The 2023 Addition includes a family history and genealogy file that consists of a family tree and correspondence between descendants regarding Larson's life and with journalist Axel Odelberg, who wrote a biography of Larson. Additional material includes correspondence from Larson to his daughter Mary and to his granddaughter Virginia, detailing news of the family and his daily life, and photographs of Larson in Mongolia, in the United States with family, and of his home in Sweden.

The letters of Mary Rodgers Larson include the oldest correspondence in the papers. Mary Rodgers was an American missionary in China from Albany, New York, who married the Swedish missionary Frans August Larson. Her earliest letters were written to Rodgers family members while she was a student at Northfield Bible Training School in Massachusetts and while doing mission work in Vermont, a time when she was contemplating life as a foreign missionary. Letters to her brother, James Rodgers, and his wife Anna Rodgers, missionaries in Brazil and later in the Philippines, date from her time as a student and when she was serving in Vermont as an "evangelist." Letters to her mother, Mary Rodgers, document her early missionary years in China and Mongolia. Subsequent letters from Mary Rodgers Larson were written to her daughter, Mary Larson Walker. The 2023 Addition includes additional correspondence from Mary Rodgers Larson to her daughter, Mary Larson Walker, and to her granddaughter, Virginia Walker Hart, concerning news of the family, daily life, her birthday and gifts. Also included is correspondence, exchanged by Mary Rodgers Larson's husband and daughter, concerning her health and plans for her care.

Material relating to Mary Larson Walker can largely be found in the 2023 Addition and includes correspondence with her husband, C. Lester Walker, prior to their marriage, friends and former classmates at the Chefoo School, and her mother. Topics of the letters include her daily life, travel between the United States and China, the growth and development of her daughter, and gifts received. The file for Mary Larson Walker also contains documentation of her nursing career, including correspondence, photographs and a scrapbook dating from her time as a nursing student at Rochester General Hospital, and records of her marriage and immigration and naturalization in the United States.

Another large portion of the family papers is the file for C. Lester Walker, husband of Mary Larson Walker. They met in China while he was teaching for the Yale-in-China program and she was working as a nurse for a hospital in Beijing, China. Walker later returned to China as a war correspondent during World War II. His file contains some correspondence but is primarily composed of drafts of writings dating from the 1940s to the 1980s. The writings kept in these papers focus on China-related topics, both fiction and nonfiction. The 2023 Addition includes additional material dating from his time as a war correspondent, including photographs and correspondence with various members of his family relating details of his work, daily life, travel, the end of the war, and censorship. Also included in the 2023 Addition are photographs of his childhood and early adulthood, including at Camp Durrell, in Friendship, Maine, Phillips Exeter Academy and Yale University, and his early life and wedding in China. Images of his later life and family include portraits and photographs of his siblings and extended family, and of trips to Capri, Italy, Puerto Vallarta, Mexico, Rhodes, Greece, Nova Scotia, Canada, and Hawaii. Also present is biographical information, correspondence and documentation relating to his attempts to secure a commission in the United States military in 1943, and correspondence with his father, Charles Arthur Walker, his mother, Ada Whitmore Walker, and with his wife, Mary Larson Walker, relating details of his daily life, travel, health, marriage, finances, and business dealings.

Photographs in the papers are primarily in the photographs file and in the photograph albums, but also can be found in other folders as attachments. The photographs cover the entire date range of the family papers and include family portraits, including extended members of the Rodgers family, and images from Sweden, the United States, Canada, China, and of Mongolia, where the photograph collection is particularly strong. Frans August Larson served as expedition guide in Mongolia for the American naturalist and explorer Roy Chapman Andrews (the 1923 expedition that discovered dinosaur eggs and fossils) and for the Swedish geographer and travel writer Sven Anders Hedin (in 1927). Photographs from both expeditions are present, but the Hedin expedition is especially well-documented. Other photographs from Mongolia present images of landscapes, animals, daily life, special occasions, and Mongolian friends. Diluwa Khutugtu Jamsrangjab, a Lamaist dignitary and a Living Buddha, referred to as Delwa Gegen by Larson, appears in photographs and is frequently mentioned in letters. Photographs of China include the family's home in Kalgan. Also of interest is Mary Louise Larson Walker's photograph album from around 1915 featuring The Chefoo School, Chefoo, China, where she was a student. Chefoo was a boarding school for children of Christian missionaries and other westerners in China. The 2023 Addition contains additional photographs filed under individual family members and includes portraits, images of daily life, and family reunions.

Many of the individuals represented in the papers were also involved in mission work and provide additional perspectives on missionaries in East Asia. Folders often have a handful of letters and perhaps some photographs or a news clipping, but researchers should bear in mind that individuals that have slim folders will also appear in photograph albums and will be discussed in the family correspondence. For example, the folder for Eleanor and Owen Lattimore holds three letters by Eleanor to Mary Larson Walker and one from Owen to Mary's brother James plus an article by Owen Lattimore, but there are items in the photograph files, and frequent descriptions of meetings with Owen Lattimore in Frans August Larson's letters to his daughter. Although not focused on the Larsons, the Kalgan Mission Reports summarize yearly missionary activities, 1896-1900. The file on Ruth Ingram, in addition to a news article about the murder of her husband, a missionary doctor in Kalgan, and some personal correspondence, includes a set of lengthy mimeographed letters sent to friends providing detailed information on her work with nursing schools for UNRRA in China and Burma, 1946-1951. Also of interest is the file on writer Nora Waln, who assisted Larson with the writing of Larson, Duke of Mongolia. The file includes an article describing her first meeting with Larson. Finally, many of the letters in the collection are from the years after the family left Asia and concern life in the United States primarily in Alabama, California, and Connecticut, and on Vancouver Island, British Columbia, Canada. The letters relate Frans August Larson's and Mary Rodgers Larson's short-lived venture as chicken farmers in Alabama, Mary's difficult onset of dementia and her passing, Frans August Larson's triumphant trip to Sweden as the famous Duke of Mongolia, and his final years in California and British Columbia. Throughout his correspondence, he returns again and again to thoughts of Mongolia. Due to Cold War political realities, he was never able to return.