March 5, 1970: The Nuclear Non-Proliferation Treaty goes into effect, with its 43 member-nations agreeing to oppose the spread of nuclear weapons or the sharing of nuclear weapons technology.
March 5, 1993: The U.S. Environmental Protection Agency (EPA) extends its emissions-trading scheme to cover sulfur dioxide pollution, a key component of acid rain.
March 5, 1998: Lake Champlain (at right) is designated the "Sixth Great Lake," joining the much greater other Great Lakes. Champlain straddles the border between New York state and Vermont. It’s hundreds of miles from the nearest and smallest of the original Great Lakes, Ontario, which has 20 times the surface area of Champlain. Vermont Sen. Patrick Leahy sought the designation to give Champlain a better shot at scoring federal Great Lakes funds. The designation was later rescinded.