Some of the churches in Saginaw have web sites, and on those sites they may include brief histories of the church. I’ve linked to those pages here
Lutheran Churches in Saginaw - scanned ebooks for download:
Holy Cross - published in 1949
Trinity - published in 1935
St. Johns Episcopal - published in 1943
Evangelical Lutheran Churches in Saginaw County - 1922
Biographical directory of Evangelical Lutheran pastors 1870-1956 - published in 1952
St. Lorenz Lutheran, Frankenmuth
St. John’s Lutheran - records from 1856 to 1862
Immanuel Lutheran - Frankentrost