Question: copyright expirations

I am wondering if Susan B Anthony's Addresses Judge Ward Hunt in 'The United States of America vs. Susan B. Anthony' which is reprinted in 'Voices of a People's History (ed. Howard Zinn & Anthony Arnove) is something we need permission to reprint? Also wondering what the rule is, regarding writings over 50 years old, or 100 years old -- I have heard both.