How old is the Pentecostal Holiness Church?

Answer 1

The age of Holiness Pentecostal church is undetermined. But, the first congregation of Pentecostals, was also the first congregation of Christians. In the Upper Room was the first sanctuary, where Jesus told his followers to tarry. So, It's been awhile. :]

How we figure they're Pentecostal is they follow the signs. As do all Pentecostal churches.

By the way: Pentecostal comes from the day of Pentecost. The day when the Holy Ghost came from Heaven.

Answer 2

The founding of the actual church in the US and UK is cited in the handbooks of each. Below is the quote from both:

During the last 21 days of the 19th century, a band of earnest, hungry-hearted ministers and Christian workers in Bethel Bible College, Topeka, Kansas, called a fast, praying earnestly for a great outpouring of the Holy Spirit, which, to their joyful surprise, came upon them in the early hours of the morning, on January 1, 1901. The people were heard speaking in other languages as the Holy Spirit gave them utterance, just as it had happened on the day of Pentecost in the year 30 A.D. A great revival immediately broke forth, which soon reached to the state of Texas, and thence west to Los Angeles, where in the year 1906 it centred in an old building on Azusa Street. Ministers and evangelists gathered in Los Angeles from every section of the United States and Canada, and missionaries returned from the foreign fields to learn more about this new experience.

Many who came were soon filled with the Holy Ghost. From here it spread throughout the whole earth, penetrating even into the heathen darkness of India, Africa, China and the isles of the sea, thus fulfilling the great commission of our Lord: "...go ye into all the world and preach the Gospel to every creature."

With the coming of the Holy Spirit, the word of the Lord became a new book. Truths which had been hidden for many years were made clear. In the year 1914, came the revelation on the name of the Lord Jesus Christ. The pivotal doctrines of the absolute deity of Jesus Christ and the baptism in His name became tenets of faith. God marvellously confirmed our message as the Gospel was preached in its fullness. The power which was hidden in the name of Jesus began to be revealed. Literally thousands were re-baptised into the name of Jesus Christ, and multitudes received the baptism of the Holy Spirit while in the water. Great numbers were healed of incurable diseases; demons were cast out as in the days of the Apostles. In many cities where this message had gone, the report of the Samaritan revival was duplicated.

In 1944 the Pentecostal Assemblies of Jesus Christ and the Pentecostal Church merged to become the United Pentecostal Church.