Public transit can be extremely valuable for a city’s economy - in New York City 85% of the people who travel into the business district below 61st Street take some form of public transportation. In several major cities - New York, Boston, Washington, D.C., and San Francisco - the subway and other rapid rail systems are key contributors to the prosperity of the city. In NYC for example, more than $37 billion of the Metropolitan Transportation Authority’s $54 billion budget goes to subways. But building subways in the U.S. is very expensive. In fact, it’s the sixth most expensive country to build rail transit in the world. And even that is likely an understatement. High labor costs, overbuilt tracks and stations, and onerous regulations all jack up costs. NYC’s sheer population density makes it rather worth it - so many people ride the subway that the cost per rider is comparable to many European cities where total expenditures are substantially lower. However, the high costs hurt the case for public transit in less dense areas of the country. Lowering those costs could go a long way toward building affordable and accessible public transit for smaller cities around the country and reducing traffic congestion, pollution and traffic accidents.

Jeanne Gang, arguably the most important female architect working today, heads her own firm, Studio Gang, which is pushing the boundaries of the good that architecture can do, for connecting communities and for the environment. Gang talked with correspondent Martha Teichner about her most recent project, an expansion of New York's American Museum of Natural History, and about the skyscrapers, airport terminal, and other civic spaces she has designed in her hometown of Chicago meant to transform spaces, outside and within.

New York City had the worst air pollution in the world on June 6 when smoke from Canada's wildfires covered the area.