If you voted against the original grant from the foundation and your opposition is recorded in the minutes, you should have no responsibility for the grant even if it was illegal.  You do have responsibility for the financial statements of the foundation as long as you are treasurer and their attempt to keep information from you is both petty and improper.  You have a right to, and the need for, the information to fulfill your fiduciary duty.

Since the society’s board has essentially ratified the application for $75,000, it seems that the grant was not improper.  I assume that the historical society’s board made a conscious decision to approve the subsequent transfer of the property to the other organization.  If you voted against the transfer from the historical society, you would have no accountability for this transaction either. Even if you didn’t vote no, since all of the transactions are between different charities, it is not clear that the transfer would be illegal, even if the board of the society didn’t know who was on the board of the recipient. 

You may decide you don’t like working with this group, but it doesn’t look like you are accountable for anything other than the financial statements of the foundation.