Halesowen was an ancient parish that was a detached part of Shropshire surrounded by Worcestershire and Staffordshire, until the Counties (Detached Parts) Act 1844, when it was incorporated back into Worcestershire after an absence of nine-hundred years. It became an urban district in 1894, and received municipal borough status in 1935. (Source:Wikipedia)
Halesowen (originally called Hale Manor) was a medieval parish in the West Midlands region of England.
The townships of Halesowen, Cakemore, Hasbury, Hawne, Hill, Hunnington, Illey, Lapal, Oldbury, Ridgacre, Romsley and Warley-Salop formed a detached part of Shropshire; the rest of the parish, consisting of the chapelries of Cradley and Frankley, and the hamlets of Lutley and Warley Wigorn, was part of Worcestershire.
There is an map drawn circa 1814 in [https://en.wikipedia.org/wiki/Halesowen_%28medieval_parish%29 Wikipedia which shows Halesowen and Dudley as detached parts on either side of the Worcestershire/Staffordshire/Shropshire border.