I planted Joe Pye Weed for the first time ever this Spring, and they seem to be doing well, about 3 feet tall and bushy. I knew they grow tall and thought they would eventually get there. But yesterday I saw some in a garden and they are about 6 feet tall at least! Are mine on a normal growth pattern for the first year?

Your Joe Pye Weed needs a season to develop an extensive root system before it puts out a lot of topgrowth. The old gardeners' adage is, the first year the plant sleeps, the second year, it creeps, and the third year it really takes off and leaps.
Your Joe Pye Weed is a terrific native plant that practically thrives on neglect, and it will live up to its name and eventually grow like a weed with little or no fuss from you. It does become pretty leggy when it gets tall, though, so trimming it back two or three times early in the season will give it a nicer form and keep it from flopping. It won't be as tall, but it will look nicer.
Tina
JoCo Extension Master Gardener