Hall Ski lifts was founded by ski lift pioneer Victor Hall in Watertown NY.
In 1966 Hall entered into a marketing agreement with Pohlig-Heckel-Bleichert of 
Koln, Germany was a leader in European lift design. In the late 80's Hall was
purchased by Von Roll who continued to use many Hall designs in the US. Von Roll
was eventually purchased by Doppelmayr who merged with CTEC/Garaventa to form 
Doppelmayr/CTEC.  Halls are still considered very strong lifts and can be seen 
running throughout the country today.  They are one of the most desireable used
lifts.  Below is a 1966 PHB/Hall skycrusier gondola brochure.

The following is from a former Hall Employee:
There was never a merger of the two companies. However there was a marketing agreement, wherein Hall agreed to market PHB detachable and reveersible systems in North America and PHB agreed to attempt to market T-bars and chairlifts in Europe. I believe a few 'Hall' T-bars might have been built using the tubular sticks in Germany, but not very many, if any. However Hall did sell several detachable systems in the U.S., starting with Loon Mountain's system in 1966 (now at Lutsen, MN). Each successive system built in the U.S, used more and more U.S. components over time, with the last one jointly made (High Wallowas, Oregon) used only Grips and sheaves from PHB.
The last Gondola made by Hall was Sterling Vineyards in California, and used zero parts or engineering from PHB, as the grips came from another manufacturer. They were the same principle and looked identical, but were not the same. Hall's arrangement with PHB came after PHB's arrangement with Constam ended upon Ernest Constam's death. PHB and Constam sold several systems in the U.S., including Squaw Valley and Sierra Blanca  (now Ski Apache), Park City 1 and 2; and Sugarloaf 1 and 2 in Maine.

Next is a 1968 Hall chairlift brochure, the counterpart to the skycrusier brochure. This
Brochure thanks to Mark D.