Oldest doghouse

[traffic light guy]

I'm guessing the oldest doghouses would be in Pennsylvania during the mid-1970s
http://s29.photobucket.com/user/Macsignals/media/Delaware%20Lehigh%20and%20Skuykill%20River%20Valley%20Signals/Levittown/100_1969.jpg.html?sort=3&o=29

[Rick1962]

The first ones I remember seeing were in Springfield, Missouri in 1976.

Kindle Fire 2

[Big John]

There was one in De Pere, WI in the early 70s.  I remember it as "that funny looking light".  It only lasted a few years and I had not seen another doghouse signal in Wisconsin until that new installation in Eau Claire.

[traffic light guy]

I've also seen 80s Econolite Doghouses in Eastern NJ, not any other states I can think of.
As I mentioned before in PA the earliest I've seen are 12-inch eagle flatbacks on angled mast-arms, I also saw a 2nd generation Durasig doghouse and its top head stuck out further than the rest of the head.

[M3019C LPS20]

Some doghouses first appeared on certain NYC streets in the 1970s. A lot of them were manufactured by Marbelite; however, another type was Eagle Alusig.

[traffic light guy]

Some doghouses first appeared on certain NYC streets in the 1970s. A lot of them were manufactured by Marbelite; however, another type was Eagle Alusig.

Alusigs didn't appear until the 80s, oh and yes there are plenty of old Marbelite doghouses in NY and a majority of them are from the 1970s, here's an honorable mention, Delaware also has pretty old doghouses most of them are 12-8-8-8-8 Eagle flatbacks from the mid-1970s, looks like lots of states have started their doghouses in the '70s. But today the only state that still frequently uses them is PA.

[M3019C LPS20]

Alusigs didn't appear until the 80s...

The Alusig line from Eagle was in production from 1977 to 1990.

[traffic light guy]

Alusigs didn't appear until the 80s...

The Alusig line from Eagle was in production from 1977 to 1990.

It takes a while for the MUTCD to approve a signal head after it finishes production

[M3019C LPS20]

Alusigs didn't appear until the 80s...

The Alusig line from Eagle was in production from 1977 to 1990.

It takes a while for the MUTCD to approve a signal head after it finishes production

They did appear on streets before 1980, such as in areas of Michigan, like Detroit, for example.

New York City primarily installed them in the 1980s, but there are some that I believe are from the late 1970s as well (according to photographs I have studied of certain NYC intersections).