There is a total of 31380 clues beginning with on
- Only state admitted under Grant's presidency: Abbr
- Only state bordered by just one other
- Only state capital that borders another country
- Only state capital that shares no letters with the name of its state
- Only state capital without a McDonald's
- Only state capital written with a period
- Only state name beginning with two vowels
- Only state never under a foreign flag
- Only state that borders six states and Canada
- Only state which shares a time zone with Alaska
- Only state whose entire east and west borders are rivers
- Only state whose name starts with two vowels
- Only state with a majority population belonging to a single church
- Only state with a non-rectangular flag
- Only state with a nonrectangular flag
- Only state with a nonrectangular state flag
- Only state with a swallowtail flag
- Only state with a three-word capital
- Only state with a two-vowel postal code
- Only state with homonyms
- Only state with two Ivy League schools
- Only Stratego piece that can take a marshal
- Only Stratego piece with a letter on it
- Only Super Bowl the Eagles won
- Only Super Bowl won by the Jets
- Only Super Bowl won by the New York Jets
- Only supplier
- Only surviving major character in "Hamlet"
- Only tavern in Springfield
- Only team besides the Yankees to win three consecutive World Series
- Only temporarily, scientifically speaking?
- Only tennis player to have won each Grand Slam event at least four times
- Only tennis player who has won all four Grand Slam titles at least four times each
- Only the AL uses them
- Only the best rockers could also sing this
- Only the biggest one is at every show
- Only theoretical
- Only thing between you and an open window?
- Only thing filled in on the worst Bingo card
- Only thing guitarists use w/their feet
- Only thing left in Pandora's box
- Only thing that doesn't fit in
- Only thing that should be on a pitcher's mind?
- Only things Noah could afford to take?
- Only this, and nothing else
- Only this
- Only three-letter astrological sign
- Only three-letter constellation other than Leo
- Only three-letter element
- Only three-letter scale note
- Only three-letter sign of the zodiac
- Only three-letter word in Scrabble that requires both blank tiles
- Only three-letter zodiac sign
- Only three-time entrant in the Rock And Roll Hall of Fame
- Only three-time inductee into the Rock and Roll Hall of Fame
- Only three-time Super Bowl MVP
- Only tree in the Monty Python sketch "How to recognise different types of trees from quite a long way away"
- Only Triple Crown winner who wasn't Horse of the Year
- Only trisyllabic rainbow color
- Only tropical national park in U S
- Only two alphabet letters have them
- Only two helpings of pie
- Only two US states, Wash and Cal, are entirely within this zone
- Only two-time tennis Grand Slam winner
- Only U S active volcano
- Only UN member whose flag is not rectangular
- Only UN member whose name comes alphabetically between P and R
- Only UN member whose name starts with Q
- Only US city bordered by two national parks
- Only US coin that does not explicitly indicate how many cents it’s worth
- Only US marsupial
- Only US pres to resign
- Only US president also to serve as chief justice
- Only US president born in 30-Down
- Only US president born in Hawaii
- Only US President born in Illinois
- Only US president elected under the Federalist Party
- Only US president to have his portrait on a coin during his lifetime
- Only US president to have three veeps
- Only US president whose surname is more than 50% vowels
- Only US president with a star on the Hollywood Walk of Fame
- Only US senator with a unit of measure named after him
- Only US state in which the name of the state and its capital share no letters: Abbr
- Only US state motto in Spanish
- Only US state whose flag isn't rectangular
- Only US state with a non-rectangular flag
- Only US state with a pennant-shaped flag
- Only US state with a Spanish motto
- Only US state with a three-word capital
- Only US state without a rectangular flag
- Only US vice president born in Maryland
- Only unanimous Baseball Hall of Fame electee
- Only unanimous Cy Young Award winner between Dwight and Randy
- Only unanimous inductee at Cooperstown
- Only ungulate that mates in the seated position
- Only United Nations member whose name starts with "O"
- Only US president to receive both a Purple Heart and a Pulitzer Prize
- Only US president with a star on the Hollywood Walk of Fame
- Only US state that can be typed on one row of the QWERTY keyboard
- Only US state with a diamond mine