"Known but Not Common"

Some people like 'unique' names; some prefer solid classics. In my experience, though, most parents are searching for that elusive name that everyone recognizes but no one is using. This can lead two ways--a famous name that few use because it's inextricably linked to one figure; or, even more difficult, a name that is consistently underused. Never super-popular, but never out of style; it's the hardest sort of name to pin down.
But, of course, I have to try anyway, so here are names that have continuously been in the US top 1000 for the past 80 years, but have never broken the top 100 (yet! Asterisks indicate names that are more popular now than they've ever been).

This list has gone through many changes since its publication in 2012; see notes!

Boys:

• Abel*
• Abraham
• Alfredo
• Alonzo
• August
• Avery*
• Blaine
• Brooks*
• Bryant
• Byron
• Calvin
• Clark
• Clay
• Clayton
• Clinton [as of 2015, Clinton is out of the SSA Top 1000]
• Conrad
• Cyrus
• Dallas
• Damon
• Davis
• Dexter
• Donovan
• Duncan [as of 2019, Duncan is out of the SSA Top 1000]
• Edgar
• Eduardo
• Elias* [as of 2015, Elias is now in the SSA Top 100]
• Elliot*
• Ellis
• Emmett*
• Enrique
• Ernesto
• Everett* [as of 2018, Everett is in the SSA Top 100]
• Felipe
• Felix
• Francisco
• Grady*
• Graham*
• Grant
• Guillermo
• Harley
• Harrison*
• Hector
• Hugh (okay, I cheated here; it did fall from the Top 1000 for one year--2008)
• Israel
• Jasper*
• Jean [as of 2012, Jean is out of the SSA Top 1000]
• Jefferson
• Julio
• Julius
• Kendall [as of 2019, Kendall is out of the SSA Top 1000]
• Lane*
• Lincoln* [as of 2014, Lincoln is now in the SSA Top 100]
• Malcolm
• Manuel
• Marcel
• Mario
• Marshall
• Maurice
• Miles* [as of 2018, Miles is now in the SSA Top 100]
• Morgan
• Moses
• Nelson
• Noel
• Orlando
• Oscar
• Pablo
• Preston
• Quentin
• Rafael
• Ramon
• Raul
• Reginald
• Reid*
• Ricardo
• Roderick [as of 2013, Roderick is out of the SSA Top 1000]
• Roland
• Roman* [as of 2016, Roman is in the SSA Top 100]
• Ross [as of 2013, Ross is out of the SSA Top 1000]
• Ruben
• Rudy
• Salvador
• Saul
• Sidney [as of 2014, Sidney is out of the SSA Top 1000]
• Silas* (fell from the Top 1000 for 1967)
• Simon
• Solomon
• Sterling
• Terrell [as of 2019, Terrell is out of the SSA Top 1000]
• Thaddeus (fell from the Top 1000 for 2009)
• Toby
• Vaughn [as of 2018, Vaughn is out of the SSA Top 1000]
• Wade 
• Wilson
• Winston
• Zane*

Girls:

• Adrienne [as of 2019, Adrienne is out of the SSA Top 1000]
• Alma
• Aurora* [as of 2015, Aurora is now in the SSA Top 100]
• Bridget
• Camille*
• Carmen
• Cecilia
• Celeste
• Celia
• Claudia [as of 2019, Claudia is out of the SSA Top 1000]
• Corinne
• Daphne (fell from the Top 1000 for 1938)
• Elisa
• Elise*
• Elsa
• Genevieve
• Georgia
• Gwendolyn
• Helena (fell from the Top 1000 for 1992)
• Hope
• Iris
• Ivy* (fell from the Top 1000 for 1946) [as of 2018, Ivy is now in the SSA Top 100]
• Joy
• Juliana (fell from the Top 1000 for 1936)
• Lena
• Lucia*
• Marina
• Mercedes [as of 2015, Mercedes is out of the SSA Top 1000]
• Meredith
• Miriam
• Nina
• Nora* [as of 2013, Nora is now in the SSA Top 100]
• Priscilla
• Rosa
• Sonia [as of 2015, Sonia is out of the SSA Top 1000]

(I probably should have expected this, but I'm totally shocked by how much longer the boys' list is than the girls. Holy crap!)