According to an interactive map from Jonathan Soma, they’re everywhere.
Single men outnumber single women across the country up until age 35.
From age 35 onward, the balance starts shifting toward more single women until about age 50, where single women strongly outnumber the men.
Play around with the interactive version here and see for yourself. You can adjust the slider to change the age range.
Note: From what I can tell ‘single’ here means ‘never been married’, rather than ‘not currently in a relationship’.