Houston Astros was my pick. The picture linked above is my memory.
I voted before looking at the comments, and now I feel sort of odd that I picked the Astros. My prime baseball card collecting years were 88-92, but I was most heavy into the 90-92 sets. So all of my Nolan Ryan cards (my source for following non-Indians baseball) except the Topps '88 would have been Ryan as a Ranger.
Still, my first thought was “Astro” so that’s how I voted. I guess maybe because the Astros were better in the 80s than the Rangers were in the 90s? I dunno.
Astros. He was playing with the Angels when I started watching baseball, but I got Reds broadcasts when I was a kid and so I got to see him on a pretty regular basis with the Astros since both teams were in the NL West.
I would probably put him in the HoF as an Angel though. I think he had his best years there.
Angels.
But then the 70s were my prime years of fandom.
There was some SI cover of him in, what, 1974? Ryan in the middle of his motion, close up and looking so ferocious and powerful that I remember wanting to duck just looking at the picture.
1975, actually. Here’s a link to the cover shot.
http://sportsillustrated.cnn.com/vault/cover/featured/8438/index.htm
Houston Astros - I would provide a picture link, but anyone who has ever seen those multi-colored uniforms still has them stuck in their memory!
I have to say “other”.
Nolan’s wife is on my tennis team, so when I think what team I associate with Nolan, I have to say My Team! 
Rangers. Born 1988 and had a video about the Ryan Express that I think was produced by the Rangers, made before he retired.
But I also associate him with my team because what he’s done with the front office stuff.
The first time I heard Ryan’s name, he was with the Mets - hence my vote.
I picked Astros.
I only vaguely followed baseball until around 1978 or so. While Ryan was with the Angels at that point, one of my big memories from that era was Ryan signing the million-dollar-a-year contract with the Astros, and how that gave the Astros two of the best power-pitchers in baseball (Ryan and J.R. Richard).
And, sadly, only one of the best pitchers in baseball. Even more sadly, that pitcher was the one who had the stroke.
One could use that same logic to explain the Lou Brock for Ernie Broglio deal…
I think Angels… when i was a kid i saw him pitch at Comiskey… when he warmed up it sounded like firecrackers hitting the mitt…
I think Astros. Those years were during my baseball-watching prime (late '70s to late '80s), and I paid little attention to American League teams anyway.
Angels, just because I thought he had his best years there. Of course, his not so best years were better than anyone else’s best years.
I picked Rangers, because I’ve always primarily watched / followed the AL, and his Angels days were a little before I watched a lot of baseball. But I remember him clearly when he was with the Rangers.
As has been mentioned before, but now with video. Not just any video, a full 8 minutes clip from the game, including the fight, a rewatch, the conclusion, and Ryan’s next pitch!
For this reason and many others, I chose Rangers.
I voted Rangers, because he was a Ranger the only time I saw him pitch in person.
But I’m a bit surprised by how far ahead the Rangers are in this poll. (right now, 74 Rangers, 50 Astros, 11 Angels and 4 Mets)
I voted Texas Rangers.
Thanks for the memory FlightlessBird.
Nolan Ryan pitched 2 of his 7 no-hitters in a Rangers uniform. Not too bad for only being with the Rangers for 5 seasons.
Yep, he grew up in my home town. I always think of him as an Astro because that was the point in my life when I paid a little attention to baseball.
-MDSL