Is it mutar to walk over the George Washington Bridge on shabbos? In terms of techumin
According to Shmuely Wollenberger in The Coffee Room at The Yeshiva World Rabbi Schachter held it was forbidden.
Rav Schachter and his wife used to go for walks on Shabbos. They would cross part of the George Washington bridge then stop and turn around because the bridge is farther than the T'chum.
From Gershon Dubin at http://www.ottmall.com/mj_ht_arch/v37/mj_v37i55.html#CSN
I know that the kehila in Washington Heights does not, per their rabbonim's pesak decades ago, cross the GWB on Shabbos.