Possible Clues:

• Number of quarts in a gallon
• China, our #_____ trader
• Number of times the letter 'U' appears in each of this puzzle's eight longest answers
• By the sound of it, it's for us at last
• That's too, too sound
• They may be on the floor
• Square boundary
• Chrysler 300, e.g.
• Quartet number
• ___ Corners (Western intersection of note)