Ellen Lewis Herndon, called "Nell," was born in Culpeper Court House, Virginia, the daughter of William Lewis Herndon and Frances Elizabeth Hansborough.  Her father was a naval officer who gained national renown in 1857 when he went down with his ship, the mail steamer SS Central America, along with more than 400 passengers and crew. It was the largest loss of life in a commercial shipping disaster, up until that time. Herndon had safely evacuated 152 women and children to another vessel during the severe hurricane off Cape Hatteras, but his ship could not be saved. Nell was 20 when her father died. One of her father's cousins was Matthew Fontaine Maury, another notable naval officer and explorer.
Marriage and family
Nell and Chester A. Arthur were introduced in 1856 by her cousin Dabney Herndon Maury, a friend of Arthur, in New York City. Arthur proposed to her on the porch of the U.S. Hotel in Saratoga Springs, New York after a brief courtship.
Arthur, aged 30, married Herndon, aged 22, on October 25, 1859, at Calvary Episcopal Church in New York City. The day was her father's birthdate. Arthur, who was from rural Vermont, is said to have learned refined dressing while at Union College, where he was in the debating society, and the ways of high society from her socially prominent family. The couple were known for their parties in their Lexington Avenue townhouse in Manhattan. 
A talented soprano, Nell Arthur sang with the Mendelssohn Glee Club and performed at benefits around New York. The Arthurs appeared to have a strong marriage, but it was strained by both Chester's political activities, which took much of his time, and the divided loyalties of the Civil War. While Arthur was serving in the New York militia during the conflict, his wife privately sympathized with the Confederacy, for which many of her Virginia kinfolk were fighting.
The Arthurs had two sons, one of whom died young, and a daughter:
- William Lewis Herndon Arthur (1860–1863)
- Chester Alan Arthur II (1864–1937) - He graduated from Princeton University in 1885 and went on to Columbia Law School. He became a gentleman of leisure. President Arthur on his deathbed warned his son not to go into politics. Alan Arthur traveled extensively, maintained a fine stable of horses, and relied on polo for exercise. A celebrated playboy, at age 36 he married Myra Townsend Fithian, a California heiress. The couple separated after 16 years of marriage and divorced in 1927. Eventually he settled in Colorado Springs. In 1934 he married Rowena Graves, a real estate and insurance businesswoman.
- Ellen Hansbrough Herndon Arthur (1871–1915) - Still a child while her father was president, she was shielded from the press. She married Charles Pinkerton and lived in New York City.
In January 1880, Nell Arthur came down with a cold. She quickly developed pneumonia and died two days later on January 12, 1880 at age 42. She was buried in the Arthur family plot in Albany, New York.
The president's sister Mary Arthur McElroy served as hostess and unofficial First Lady for Arthur's social activities as president. She also cared for the Arthur children, who were then 16 and 9 years of age.
Arthur deeply mourned the death of his wife. After taking office as president, Arthur, who could see St. John's Episcopal Church from his office, commissioned a stained glass window dedicated to his wife at the church. He had it installed where he could view it at night, as the lights were kept on within the church. In addition, he ordered fresh flowers placed daily before her portrait in the White House.