You'll have to be flexible with travel dates, and there are some periods of blackout dates. Travel days will vary, you will have the best luck with Tuesday, Wednesday, and Saturday departures.
Searching on AA.com, I found seats departing CHS on Thursday, October 25 and returning from SEA on Tuesday, October 30, 2018. Other dates are scattered throughout October and through mid-December.
If you have another destination in mind, we've got you covered with this long list of fare deals from Charleston (CHS) here.
Don't be sleepless in Seattle, here's a list of available hotels for the mentioned dates on Hotelwatchdog.