Peterson Sullivan LLP Share: Accounting Peterson Sullivan LLP Visit Website 601 Union Street Suite #2300 Seattle, WA 98101 (206) 382-7777 (206) 382-7700 (fax) About Map About Peterson Sullivan is a leading public accounting and advisory firm that serves publicly traded and closely held companies in the middle market, nonprofit organizations, and high-net-worth individuals. What's Nearby? Distance: 5 10 15 20 25 50 mi.