The top middle names for baby boys and girls over the last century are a more stable group than first names, which go in and out of fashion more dramatically and rapidly. The most common middle names, on the other hand, often honor family members or provide a smooth bridge between first and last names, so they're a less diverse group.
For girls, the top middle names of the last hundred years are Marie, Ann (and Anne), and Elizabeth. For boys, Michael ranks as the top middle name of the century, followed by Joseph, William, and James.
Girl middle names popular in the first half of the 20th century that later faded away include Irene, Mae and May, and Ruth. After 1950, middle names for girls that rose to prominence include Kay, Sue, and Renee. After the year 2000, Rose, Grace, and Faith became popular middle names for girls.
For boys, middle names popular before 1950 include Henry, Francis, and Eugene. After 1950, Lee, Ray, and Wayne came into use. Lee remained popular as a middle name for boys after the year 2000, when Alexander and Matthew also came into play. 
Here, based on official records, are the top middle names for babies in the US for the past 120 years.

Top Middle Names

Much-used midcentury diminutive, now fallen far from favor even as a middle name. 

Kay, a cigarette-smoking, nightclubbing name of the 1930's, could be ready for a comeback along with cousins May/Mae and Ray/Rae. 
 Kay has been out of sight since the mid-eighties, but was in the double digits from 1936 to 1945, attached to several glamorous actresses of the period, such as fashion plate Kay Francis, as well as Eloise author Kay Thompson.
 Kay was also once a unisex name, as in Sir Kay, in Arthurian legend one of the Knights of the Round Table.
 Bottom line: Parents in search of a fresh, more cosmopolitan alternative to Kate might consider Kay..

Originally a feminine of John, Jean was popular in Scotland long before it found favor elsewhere, and had its most shining moment here in the era of Jean Harlow (born Harlean), ultimate symbol of silver screen glamour. Now, though there are many grandmas and even moms with the name, it doesn't seem all that baby-friendly. Though that could change, and Jean could join Jane.
 A perennial on the popularity list until it finally dropped off in 1994, Jean was in the Top 20 from 1922 to 1936 and ranks among the 100 most <a href="/list/653/100-most-common-names-for-girls">common names for girls</a> of the past century. It was extremely well-used as a middle name, as in Michael Jackson's song "Billie Jean" and tennis champ Billie Jean King, not to mention Hermione Jean Granger from Harry Potter/. It was also the actual first name of Scout Finch in To Kill a Mockingbird. Maggie Smith shone in the 1969 film The Prime of Miss Jean Brodie, and nickname Jeanie was commemorated in the Stephen Foster classic song "I Dream of Jeanie with the Light Brown Hair," as well as in the early sitcom, I Dream of Jeannie.

Jean

Lynn arrived in the 1940s, spinning off from the wildly popular Linda to become a top mid-century middle (and first) name, ranking at #58 during its 1956 peak. Now, however, Lynn is out of the charts, more likely found stuck on to the end of another name (see Emberlynn and Gracelynn)
 
Derived from either the Welsh llyn meaning "lake", the Spanish linda meaning "pretty, beautiful", or the Germanic lind meaning "soft, tender, flexible", Lynn was used predominantly as a masculine name, right up until 1942 when it swung more feminine for the first time, chosen for 1749 girls compared to 1394 boys.
 
Still given to nearly 70 girls in a recent year, Lynn remains, quietly, on the radar at least.

Lynn

Ann, the name of the sainted mother of the Virgin Mary, was among the top <a href="https://nameberry.com/girls-names">girls’ names</a> for centuries, in both the original English Ann spelling and the French Anne. Both left the Top 100 around 1970 and show no signs of returning, with Anne is the middle of the US Top 1000 and Ann dropped out of sight. 

Once a go-to middle name, Ann has lost its stature in that position as well. Still, it's one of the most <a href="/list/653/100-most-common-names-for-girls">common names for girls</a> of the 20th century.
 Some more popular related names today include Hannah, Anna, and Annabelle.

top middle names — baby with first birthday cake

top middle names

Top middle names include popular choices such as Rose and Grace for girls, James and Michael for boys. (Page 3)