A second volume, Husfrue （The Wife）， followed in 1921, and the final volume, Korset （The Cross）， was published in 1922.
The success of her epic trilogy brought Sigrid Undset further financial security, for which she was grateful. In addition to receiving income from book royalties, she was awarded a lifetime annual author’s stipend from the Norwegian government. Success also brought fame, however, and all the intrusions this entailed. Undset had always been an exceedingly private person who zealously sheltered her children and personal life from the public eye. She had little patience for journalists and seldom gave interviews. But she could also be extremely warmhearted and generous; she responded to all the letters sent to her, and she often sent money to the steady stream of desperate people begging for help from the famous author.
With the publication of Undset’s second great medieval work in 1925 and 1927—a tetralogy entitled Olav Audunssen （published in English as The Master of Hestviken）—her status as one of Norway’s greatest writers was confirmed, and her place in world literature was unquestionably assured.
In 1928, Sigrid Undset was awarded the highest honor for her work, the Nobel Prize for Literature. It was given to her principally for “her powerful pictures of Northern life in medieval times.” At the age of forty-six she was one of the youngest recipients, and she was only the third woman to be honored with the prize.
At the time of the award, Kristin Lavransdatter had been translated into many languages and was widely known around the world. In Germany alone, there were 250,000 copies in print.
According to all accounts, Undset took the news of her award with admirable calm, although she did buy herself an elegant new dress for the occasion. At the award ceremony in Stockholm, P?r Hallstr?m, author and member of the Swedish Academy, gave the presentation speech. He praised Undset’s early novels, in which she depicted modern women “sympathetically but with merciless truthfulness … and conveyed the evolution of their destinies with the most implacable logic.” He then paid tribute to her brilliant recreation of medieval life in Kristin Lavransdatter and The Master of Hestviken, and to her profound insight into the “complex relations between men and women.” Sigrid Undset graciously expressed her thanks for the honor but declined to make a speech, explaining that she was a writer, not a speaker.
The prize was then worth 156,000 kroner, and Undset gave it all away. Part of the money went to the scholarship fund of the Norwegian Writers Union, but the bulk of the award was divided up to establish two foundations. The first would provide support to Norwegian families with mentally retarded children who needed financial assistance to care for their children at home. This was something that Undset had dreamed of doing for many years, and the stipend was named the Maren Charlotte Undset Svarstad Grant, in honor of her daughter. The other foundation was established to provide financial aid to needy Catholic children in Norway who wanted to attend parochial schools.
Eleven years later, when the Soviets invaded Finland, Undset would sell her gold Nobel medallion for 25,000 kroner and give the money to the relief effort for Finnish children.
During the 1930s, Sigrid Undset’s life was a whirlwind of literary activity. As a world-famous author, she was much in demand. She served two terms as president of the Norwegian Writers Union and attended an endless number of meetings and functions associated with this role. She continued to write articles and reviews, and she published four more novels, several collections of essays, and an autobiographical novel based on her childhood entitled Elleve aar （translated into English as The Longest Years）。
At the same time, she continued to care for her daughter and manage the household in Lillehammer with the help of her long-time housekeeper. At Bjerkeb?k, Undset always gained some measure of peace by escaping the demands of everyday life to work in her garden. Ever since she was a child, Undset had been an avid botanist. As an eighteen-year-old she described in a letter her love of nature as “that hypnotic immersion in the corolla of a rose when you have stared at it for so long that all outlines are erased and you become dizzy with crimson.” She said that she longed to “disappear into nature so that you cease to feel or think, but with all your senses you greedily draw in the light and colors, the rustling of leaves and the trickling of underground streams, the sun and the shifting shadows—that is happiness, nirvana.”
Undset’s love of nature so permeated her world view that it became synonymous with the truth she sought to portray in her novels, the truth that her mother had enjoined her to write about. In a speech given during the 1940s she explained what she meant by a “true novel”： We often see the word “novel” defined as the opposite of “facts.” And of course those kinds of novels do exist. But even those types of novels do not necessarily have to be the opposite of “truth.” Facts may be true, but they are not truths—just as wooden crates or fence posts or doors or furniture are not “wood” in the same way that a forest is, since it consists of the living and growing material from which these things are made… The true novel, if you understand what I mean by that term, must also make use of facts, but above all it must be concerned with the truth that lies behind them—the wild mountains that are the source of the “tame” cobblestones of the pavement or the artistically hewn stones in a work of sculpture; the living forest which provides timber for the sawmills and pulp for the billions of tons of paper which we use and misuse. Then these facts will be of secondary importance to the author… they are not original; they originate from something else.