Trinity was formed in April of 1942 when the Fairview Mission Church voted to officially change their name to Trinity Evangelical Lutheran Church under the leadership of Pastor Lawrence Schreiber. The church originally met across Arthur in the Fairview Public School building (now the West Allis Recreation building). In December 1942, Rev. Elmer Rimpler was installed as the first full-time pastor at Trinity. In May 1944, Rev. F.H. Gehrke became pastor. By this time, Trinity had out-grown the Fairview building and in 1945, plans were made for a new, permanent church building. The cornerstone for the church was laid on September 28, 1947. By 1952, the membership had grown again and the church began to have two services each Sunday. In 1955 the church council voted to take on an expansion of the 1948 building. By 1957, the church had raised enough in internal pledges that a loan was secured and the expansion project was began. Construction began in the spring of 1957. The Lord continued to bless Trinity with growth and by 1966, the communicant membership had grown to 859. Worship space once again became an issue along with classroom space to host the 27 different Sunday school classes held each week. In 1969 the church once again looked into an addition to the church. On September 7, 1970, a groundbreaking ceremony was held for the new education unit for the church. The building project was complete and dedicated on September 12, 1971. In 1978 a new organ was installed into Trinity to enhance the worship life of the congregation. On December 23, 1979, the church celebrated the final payment of the building debt. Pastor Gehrke celebrated his 40th year at Trinity on October 2, 1983. In 1987, the church garage was completed, housing all of the maintenance equipment for the upkeep of the church and its grounds. Pastor Gehrke officially retired on June 9, 1991 after 47 years of faithful service. Rev. Thomas Krueger was installed as pastor on October 13, 1991. In October of 1992, Trinity celebrated its 50th Anniversary. The Trinity Lutheran School had grown to encompass pre-school through first grade. Pastor Krueger retired after 26 years of ministry at Trinity on July 17, 2017. Rev. Brandon Koble was ordained and installed as Trinity’s fifth pastor on August 27, 2017. In December of 2021, Trinty and Oklahoma Avenue Lutheran Churches formed a dual-point parish, working together under the leadership of one pastor to serve the community of West Allis and Milwaukee.