Yup - Eastern Redbud - Cercis candadensis. Odd name considering its native range does not technically touch Canada. Is that pic from today?

I don't think it's Tilia henryana. Typically the "spines" of the soft spine like teeth are much longer on T. henryana than the leaves in the photo. You can find T. americana(Basswood, American Linden) with leaves with small soft "spine" like teeth like the leaves in the photo. The leaves look too large for T. henryana, which top out at about 4"x4"(10cm x 10cm), to me also. They look much closer in size to T. americana, which range from 4"x4" on the small side up to 8"x8"(20cm x 20cm), to me. Also, T. henryana in cultivation has so far been a relatively small tree in the 30' to 35' range(roughly 10m). Lastly, I'm doubtful that T. henryana(considered zone 7 hardy usually) is hardy in the zone 5 Brookfield Zoo which has seen temps as low as -20°F(-29°C) within the past 12 years or so(surely within the lifetime of this tree). So, I believe this is a Basswood tree(T. americana).

Hybrids between those two species sometimes occur among batches of seedlings collected from plantings where both are present. I have seen them among blocks of seed raised stock supplied to retailers here, usually I guess as Stewartia pseudocamellia. Also there has been a history of the hybrid (S. x henryae) being cultivated mistakenly as S. sinensis in the past. Closer views of this planting, preferably at flowering time needed for the most reliable responses to be generated here. Individual stewartia plants are identified to the species level using specific bark, leaf, flower and fruit characters.

Looks like redwood to me. Sequoia sempervirens.