In Washington, it is illegal for an adult (someone 18 or older) to have sex with a minor (someone younger than 16), even if the sex is consensual. The state also forbids certain sexual contact and intercourse between minors who are more than a certain number of years apart in age.
Can a 17 year old date a 23 year old in Washington State?
As the other answers point out, it may technically be legal for a 23 year-old to have sex with a 17 year-old, because the age of consent in Washington is 16.
Is there a Romeo and Juliet law in Washington?
Because Washington does not have a Romeo and Juliet Law, it is illegal for anyone under sixteen years of age to participate in any sexual activity, even if the couple is close in age.