Providing Residents in King County, WA and Surrounding Areas with Quality Landscape Supplies. Enhance the appearance of any property with quality landscape supplies from Eastside Topsoils. The residents and contractors of King County, Washington, have used us as a trusted source for all their topsoil, mulch, and aggregates needs. With high-quality topsoil mixes, you can help plant growth and root development. Eastside Topsoils provides residents and contractors quality products to ensure your garden and landscape looks it best. We have an array of options to choose from and will help you determine what works best for you. Contact us today at 206-949-8266 to place your next landscaping supply order.