President of the World Trade Center Association, Guy Tozzoli, discusses the planning, construction and operation of the World Trade Center.

Historian Niall Ferguson talks about the American Experience of globalization, globalization's political dimension, and 9/11 as a turning point.

Former New York governor Mario Cuomo talks about lessons learned from 9/11 and evolving toward a new civility.

Engineer for the World Trade Center, Leslie Robertson discusses architectural aspects of the buildings, including the sculptural quality, close columns and narrow windows, the skin structure, and the comparison to the Empire State Building.

Three-term mayor of New York City Ed Koch describes a moment on September 11, 2002.

Construction on the bridge began in January 1933. Workers excavated 3 1/4 million cubic feet of dirt to make way for the bridge's anchorages, one on each side of the Gate.

Chief Engineer Joseph Strauss hired a local architect, Irving Morrow, to design an architectural treatment for the bridge. Morrow would later be recognized for his aesthetic contributions: the Golden Gate Bridge's distinctive Art Deco lines, burnt red-orange hue, and the structure's dramatic lighting.

Working twelve to fourteen hours a day, Charles Ellis personally computed dozens of factors, and completed the bridge's overall design in four months. In November 1930, Strauss directed Ellis to begin the thousands of detail calculations involving suspension ropes, decks, floor beams, highway track, cables, towers, and more.

Cable spinning began in October 1935. To create the cables, Roebling developed a method called parallel wire construction. The innovative technique enabled a cable of any length and thickness to be formed by binding together thin wires. Hundreds of wires, each roughly the diameter of a pencil, were bound together into strands. Hydraulic jacks then bundled and compressed 61 strands to make a cable.

The south tower of the Golden Gate Bridge was built over a thousand feet into open ocean. To build the tower, workers would have to erect a pier more than 1100 feet out in the middle of the Gate -- the first bridge support ever constructed in the open ocean. Divers guided beams, panels, blasting tubes and 40-ton steel forms into position and secured them, striving to avoid being swept away.

The first 745-foot tower began to rise in Nov. 1933. Prefabricated sections were fit into place and then joined together by four-man rivet gangs. The heater was the boss; he brought rivets to the right temperature on a small forge, then tossed them to catchers with metal cans.

Emma Goldman's anarchist politics and outspoken activism against capitalism, wars, and the oppression of women captivated and polarized the American public for nearly thirty years.

American Anarchists in the 1880s were a small but powerful movement who advocated radical ideals of universal human equality, education for all, and an end to state government.

In June 1892, workers at the Andrew Carnegie-owned steel plant in Homestead, Pennsylvania went on strike. When plant manager Henry Clay Frick hired 300 armed guards to attack strikers, the resulting battle ended in deaths on both sides.

The Panic of 1893, a severe economic depression, created public awareness of the growing gap between the rich and the poor. Emma Goldman organized demonstrations and encouraged unemployed Americans to demand jobs and food from the wealthy.

In May 1917, Emma Goldman and Alexander Berkman organized demonstrations protesting America's recent entry into World War I — risking fines and imprisonment as President Woodrow Wilson's administration increasingly cracked down on anti-war resistance.

Emma Goldman defied laws against public discussion of sex and contraceptives, campaigning for birth control as a means of social change and women's empowerment. Beginning in 1908, Emma Goldman toured the country with her partner, Ben Reitman, speaking on anarchism, free love, and other controversial issues.

Psychology professor at the City College of New York, Dr. Kenneth Clark introduces the segment "The Negro and the American Promise" from Boston public television producer Henry Morgenthau III. Featuring interviews with Martin Luther King, Malcolm X, and James Baldwin, the segment made headlines in spring 1963.

Martin Luther King appears in Boston public television producer Henry Morgenthau III's "The Negro and the American Promise," alongside Malcolm X and James Baldwin.

James Baldwin appears in Boston public television producer Henry Morgenthau III's "The Negro and the American Promise," alongside Martin Luther King and Malcolm X. The New York Times described the James Baldwin segment as "a television experience that seared the conscience."