Williams College (ED)

GPA: 4.10/4.30 unweighted
SAT: 1530
EC: Lots of service clubs, lots of volunteer work, some leadership, art design club, etc.
Honors: National merit scholarship semifinalist (hopefully!), some school awards, art award (national)
Decent teacher recommendations (the teachers I asked for all nominated me for awards)
Applying with art portfolio (intended art major)
What are my chances of getting into Williams College (Early Decision)?

Welcome to College Confidential, @chickenwindow !
Congratulations on your achievements in high school!

None of the students, parents, alumni, etc. on CC are the admissions officers looking at your full application in comparison to those of all the other ED applicants, and there is no crystal ball to tell what those admissions officers will think and decide. Holisitic admissions have unpredictable outcomes, alas.

But, as you yourself can see, your excellent statistics are typical of students who are admitted. Moreover, early decision is a good strategy to boost your chances, since half the class is admitted ED. So put together the best application you can and give it a try! Good luck!

You have strong stats and your interest in art is great. It should help you stand out especially if you are well rounded in terms of leadership and activities.