From what I'm told, several decades ago one who wanted to walk from Ner Israel yeshiva on Mt. Wilson Lane in Pikesville, MD to the greater Baltimore community (e.g. Rabbi Heinemann's shul, the Agudah, 6202 Park Heights Ave) on Shabbos would require an eruv Techumin, as the two environs were deemed non-contiguous. I've also heard that this is no longer required.
At what point did this change, and exactly why? (E.g. what was built that changed it? What year was that? And who gave the psak?)