Skagit County, Washington.
Last spring, I went to Seattle to visit my cousin. We went up to Skagit County to see all of the tulip farms. It was amazing! If you ever find yourself in the Seattle area in April, you MUST make the 1 hour trip north.
We visited two tulip farms, Tulip Town and Roozengaarde. They grow daffodils, too! So if you're there early in the month or maybe even late March, you'll see the daffodils, too.