Her first paternal ancestor to arrive in America was George Marable (1631 - 1683), who traveled to Virginia from Kent, England, circa 1652 and was one of the first colonists settling in what is now Jamestown, Virginia. The Marable families of the southern United States all derived from the aforementioned George Marable.
By the time of the American Civil War, the Marable family of Jamestown, Virginia, had spread across the South. Marables are found in the rosters of units from at least nine of the Confederate States. In Virginia, Edward W. Marable of the Charles City Southern Guard served aboard the Confederate ship Patrick Henry during the engagement of the Merrimack with the Federal fleet at Hampton Roads. John H. Marable of the 13th Virginia Cavalry served as a courier for Gen. J. E. B. Stuart.
Marables have also been found in units from Tennessee, Georgia, Alabama and Mississippi, and among the dead at Gettysburg. The Marable family were wealthy southern aristocracy and as such were slave owners. Today, the majority of those bearing the name Marable are descended from emancipated slaves not George Marable.
It is from Benjamin Marable (1710 - 1773), who traveled to Tennessee, that the Gumm family is descended. The Gumm name can also be found in the registers of soldiers who fought for the Confederacy throughout Rutherford County, Tennessee.
Garland's father was Francis (Frank) Avent Gumm, the fourth of six children born in Murfreesboro, Tennessee on March 20, 1886. He died on November 17, 1935, in Los Angeles, California. His parents were William Tecumseh Gumm (1854 - 1906) and Elizabeth Clemmie Baugh (1857 - 1895). The Gumm family was a mixture of English, Irish, Scottish, French Huguenot and German.
Frank Gumm married Ethel Marian Milne, who was born on November 17, 1893 in Michigamme, Michigan. She died January 5, 1953 in Los Angeles, California. Ethel was the eldest of eight children born to Eva Fitzpatrick (born on January 4, 1865 in Messina, New York) and John Milne (a Railroad Engineer) born October 15, 1865 in Ontario Canada. His parents were Charles Milne (born in 1829 in Arbroath, Angus, Scotland) and Mary Kelso (born 1837 in Kilmarnock, Ayrshire, Scotland).
Eva Fitzpatrick-Milne was the daughter of Hugh Fitzpatrick (1838 - 1908), whose family arrived in the United States from Smithtown, County Meath, Ireland in the 1770s and Mary-Elizabeth Harriot (born December 23, 1841 in Dublin, Ireland). Mary, one of thousands of orphans as a result of the Irish Famine, was raised in a Dublin convent. In 1858, at the age of 17, she married Hugh Fitzpatrick (an Irish-American) who was visiting Dublin. That same year, the newlyweds sailed to America. They had ten children. Mary died on January 24, 1908 in Detroit, Michigan. She was the last of Judy Garland's European born ancestors.
Eva Fitzpatrick-Milne lived with Garland until her death on October 17, 1949 at the age of 84. She is buried next to Garland's father in Forest Lawn Cemetery, Glendale CA. Garland's mother is also buried nearby in a separate grave under the surname Gilmore.
During the Revolutionary War the Fitzpatrick family fought on the side of the British. As a result, Peter Fitzpatrick (b1752 - d1812) a member of the Kings Royal Regiment of New York under command of Sir John Johnson and son of Patrick Fitzpatrick (born 1727) who left Ireland in 1766 by joining the British 8th Regiment of Foot, called Seabright's Royal Irish Regiment was sentenced to be hanged as a spy. This sentence was not carried out and the family moved across the border; eventually settling in Cornwall, Ontario, Canada. Peter was married to Catherine Warner about 1772, and had at least two sons: William Fitzpatrick - born in 1773, and Hugh Fitzpatrick born 1809. 
A family link between Garland and the 18th United States President Ulysses S Grant has often been incorrectly stated. Garland’s great, great grandfather Hugh Fitzpatrick (1809 - 1878) was married twice; his second wife was Catherine Grant, a first cousin of Ulysses S Grant. However, Garland is descended from a son, also named Hugh (born 1838), from his first wife (Margaret Ross, 1807 - 1845), therefore there is no blood link.
During the 1930s through the 1950s Hollywood studios contained a contingent of stars and contract players that were either Irish born or connected to Ireland through heritage such as; John Wayne, Spencer Tracy, James Cagney, Bing Crosby, Tyrone Power, Lucille Ball, Maureen O'Hara, Maureen O'Sullivan, George Brent, Pat O'Brien, Grace Kelly, Gene Kelly, Victor McLaglen,George Murphy and many others (Garland was included in this category). Lesser known stars such as Barry Fitzgerald, Fred Allen, Sara Allgood, Una O'Connor, Ray Bolger, Arthur Shields, Ward Bond, and Frank McHugh, director John Ford, and behind the scenes technicians and workers such as set designer Cedric Gibbons were also in this exclusive group that was sometimes referred to as Hollywood's Irish Mafia. MGM and other studios promoted and capitalized on the Irish connections of their stars through films such as Little Nellie Kelly, The Luck of the Irish, The Informer, The Quiet Man, Parnell and Darby O'Gill and the Little People among many others.
In 1951 during her first European concert tour that included performances in Ireland and Scotland Garland made reference in the press and on stage to her Irish Grandmother and her Scottish roots and she added special material to her concerts just for those performances. In Dublin she sang from her dressing room window at the Theatre Royal to crowds in the street that were unable to get tickets. In Scotland she sang accompanied by bagpipes. During a guest appearance at a concert in Birmingham, England that featured Irish music and dances, she was dubbed "America's Colleen" by the press. 
When commenting on her ancestry, Garland described herself as Irish and Scottish and referred to herself during a 1963 press conference as "just an Irish biddy". She referred to her father as an "Irishman". Although part Irish Frank Gumm's ancestry was mixed, her strong Irish connection was through her maternal Grandmother and the Fitzpatrick line. Her daughter Lorna Luft stated in her autobiography "My Grandfather had an Irish charm and the family has sometimes survived on charm alone".