Phelps Dodge Corporation began sinking the three compart ment Warren shaft on January 27, 1927. The steel headframe was removed from the Lowell shaft and placed on the Warren around this time. During the first year, the shaft was sunk to the 1800 level or 1,662 ft. and connected with the 1800 level of the Calumet & Cochise shaft.  The cost at the time was $210,916.65, which is $128.53 a foot. Another $99,738.76 was spent on driving drifts to connect to the Calumet & Cochise. This diverted the water from the C&C to the Warren.  In 1928, the Warren shaft was extended another 477ft. to a final depth of 2,147ft. Stations were cut on the 900, 1800, and 2000 levels.  Later, a shaft and pump station was blasted out on the 2200 level and two 1,000 gallon per minute pumps were installed. 1929 was the height of operations at mine, 10887 ft. of drifts, and raises were driven on the 900, 1800, and 2000 levels, but no ore was found. The following year only a quarter of the development of the previous year was completed and it also failed. Only a body of pyrite was discovered. In 1931, Phelps Dodge and the Calumet &Arizona mining companies merged. With the acquisition of the rich orebodies in the Campbell and Junction mines, the urgency to find new ore was relieved and prospecting in the Warren Shaft ceased. The Warren was allowed to flood and the water soon rose to well above the 1800 level, leaving two pumps underwater on the 2200 level. In 1935 the air compressor was salvaged from the mine and transferred to the Czar Mine to be used by lessees.  Also, a concerted effort began to be made to drain the ground east of the Campbell fault in preparation for exploratory mining.  During 1937, drain holes were drilled from the 1800 level Campbell into the flooded shaft. The 2200 level Campbell was prepared to handle the significant water pouring in from not only the Warren, but also the interconnected Calumet &Cochise Shaft.  Water in the Warren shaft was lowered by 411ft. and 316ft. in the C&C shaft during the year. The draining of the eastern region continued for years particularly, since ore was being discovered in the area.  In 1940 it became necessary to retimber the top 900ft. of the shaft.  Also, Phelps Dodge was able to drain the shaft from four ft. above the 1800 level to nine feet above the 2000 level. Later, in 1942, 190 crosscut from the Campbell was driven within 48ft. of 2203 crosscut of the Warren Shaft.  This was to increase water flow from the Warren into the Campbell.  At the time, the Junction was pumping on average 6,624 gallons per minute, with a good portion coming from the Warren shaft area. During the following year the water level fell to below the 2200 level and the company removed the once lost pumps. Considerable copper ores were found east of the Campbell fault on the 2566 level of the Campbell mine. Finally, in 1946 drain holes were drilled from the 2700 level Campbell into the Warren shaft to drain it completely and eliminate the need for small pumps to be kept on the 2200 level of the Warren. This year also gave the mine a new role as a ventilation shaft. On the 1800 level, in the drift connecting to the C&C shaft, 500 feet were widened to increase air flow and a bulkhead was removed from the C&C shaft above the 1800 level. The mine was to serve as a ventilation shaft until the end of mining in 1975. The headframe (without sheave wheels) and the hoist house (without a hoist) are still standing and are located across from Greenway Elementary School in Warren. The shaft is protected by a concrete cap and the hoist house is used by the Bisbee Mining & Historical Museum for storage. Although, the mine failed to produce any mineable ore, it was useful in aiding to drain the ground east of the Campbell fault and to ventilate the deeper levels of the Campbell mine.