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"It was difficult for me to be there," Magnus admits more than a decade later. "Every time I thought that I was overreacting, something grotesque would happen."

During Yom HaShoah observances at a Cologne synagogue, a neo-Nazi protester marched, yelling anti-Semitic epithets. German archivists were helpful enough with answering her research questions but never friendly.

The worst incident occurred one day when a congregant knocked frantically on his rabbi's door. For several hours, the rabbi's wife consoled the hysterical man, who had gotten a scare while receiving a chest X-ray.

The man recounted how the X-ray radiologist had noticed the numbers branded on his arm and asked where he had gotten them. The man replied, "I was at Auschwitz."

"Me, too," the radiologist said.

Few of the Jews Magnus encountered in Cologne had any German family history preceding the Holocaust.

"Most of the Jews come from Eastern Europe and Russia, some secular Israelis," she said. "Those who returned after the Holocaust were broken people living out their lives."

Magnus spent most of her time in Cologne at the city archives, which contained one of the oldest and most enigmatic Jewish histories of any city in Europe.

She was lured to the German cathedral city, which had been home to Jews since Roman times. Few European cities had witnessed such dramatic changes in their Jewish populations. Time and again, following massacres and expulsions, Jews constantly returned to flourish in the commercial hub of the Rhineland, where they achieved unprecedented civil equality from 1798 to 1871. Magnus' research fueled a doctoral dissertation, "Jewish Emancipation in a German City," which was released as a book in April by Stanford University Press.

From the early 1300s until 1424, Cologne's Jews had been double-taxed, once by city officials and once by the archbishop. Both exercised control over Jewish civil rights in an ongoing competition for sovereignty. The Jews suffered mounting tax burdens, massacres and eventual expulsion from the city, Magnus writes in her book.

No Jew set foot in Cologne for about 400 years until 1798, when the French seized the city and welcomed the Jews back with full civil emancipation. Despite French anti-Semitism, France's revolutionary legacy resulted in equality for all its citizens.

By the 1840s, the Rhineland was on the forefront of Jewish rights in Europe. Cologne's Jews had adopted mainstream dress and speech, and worked as merchants, teachers, butchers and brokers. There was widespread perception of Jews as assimilated members of the middle class, who left separate neighborhoods to integrate into the wider community.

While Magnus maintains that emancipation resulted in the successful integration of Jews into the German middle class, the victory was short-lived. The Prussians, who inherited Cologne in 1814 after French concessions, preserved the French concept of emancipation. However, in competition for control between the Prussians and city officials, the Jews became sacrificial pawns.

Over the next 57 years, Cologne's Jews enjoyed legal equality but continued to battle anti-Semitic discrimination in their business and private lives.

Magnus says Jews responded to the double-edged sword by constantly trying to achieve social acceptance by assimilating, enjoying some degree of success.

"One thing that is clear is that it was really a complicated picture. There was profound anti-Semitism. But there also was this reality that Jews made tremendous advances there."

The author's research stops short of the late-19th-century backlash period, during which Germans began to scapegoat Jews for the social ills that accompanied the modern industrial era.

"There's no way that anybody can't wonder about the connection between [the end of emancipation] and the Holocaust," Magnus said, but then, that's another book.