Alice graduated in June 1899 and shortly after married Henry Wise Miller (October 1899). They left for Costa Rica, where he attempted to develop rubber cultivation. This venture eventually failed; in 1903, she, her husband and young son returned to New York, where they lived in difficulty for some time, he working in the Stock Exchange, she teaching, which she hated. After a time, her husband earned more and she was able to dedicate her working time entirely to writing.
She became known as a campaigner for women's suffrage and published a brilliant series of satirical poems in the New York Tribune. These were published subsequently as Are Women People?. These words became a catchphrase of the suffrage movement. She followed this collection with Women are People! (1917).
As a novelist, she scored her first real success with Come Out of the Kitchen in 1916. The story was made into a play and later the 1948 film Spring in Park Lane. She followed it with a series of other short novels, many of which were staged and (increasingly) made into films. At about the same time, her husband began to make money on the Exchange and their money problems were over.
Her marriage endured to the end of her life, but was not entirely tranquil. Her novel in verse Forsaking All Others (1933) about a tragic love affair, which many consider her greatest work, reflects this, though it is certainly not autobiographical.
In the 1920s and 1930s, many of her stories were used for motion pictures, such as Roberta (1935) and Irene (1940), taking her to Hollywood. She also became involved in a number of motion picture screenplays, including Wife vs. Secretary (1936). Her name appears in the very first issue of The New Yorker as an "advisory editor".
In 1940, she wrote the verse novel The White Cliffs. The story is of an American girl who coming to London as a tourist, meets and marries a young upper-class Englishman in the period just before the First World War. The War begins and he goes to the front. He is killed just before the end of the War, leaving her with a young son. Her son is the heir to the family estate. Despite the pull of her own country and the impoverished condition of the estate, she decides to stay and live the traditional life of a member of the English upper class. The story concludes as The Second World War commences and she worries that her son, like his father, will be killed fighting for the country he loves. The poem ends with the lines:
The poem was spectacularly successful on both sides of the Atlantic, selling eventually approaching a million copies - an unheard of number for a book of verse. It was broadcast and the story was made into the 1944 film The White Cliffs of Dover, starring Irene Dunne. Like her earlier suffrage poems, it had a significant effect on American public opinion and it was one of the influences leading the United States to enter the War. Sir Walter Layton, who held positions in the Ministries of Supply and Munitions during the Second World War, even brought it to the attention of then-Prime Minister Winston Churchill.