It is noteworthy that Brewster, known for his generosity as a philanthropist, began his career in the depths of the Great Depression as a hotel clerk in St. Petersburg, Florida. In 1933 he secured part-time employment as master in history at St. Petersburg's Cranleigh School for Boys, where he taught until 1935. Duke University awarded Lawrence a fellowship to pursue doctoral study in 1935. He preferred English history, but requirements for foreign travel and research that were beyond his means led him to elect American social and cultural history under the direction of Charles Syndnor. his 1942 dissertation entitled "The Summer Migrations and Resorts of South Carolina Low-Country Planters" was published by Duke University Press in l947.

The New Deal Works Progress Administration funded North Carolina's Historical Records Survey. The project led to a three-volume report entitled The Historical Records of North Carolina: The Country Records. Lawrence served as research editor of this project during 1938-1939, assisting Christopher Crittenden and Dan Lacy. During the following year, he held a temporary instructorship at Clemson College and upon completion of his doctorate served as instructor in history at Duke University from 1942 to 1945.

In 1945 Brewster joined the faculty of East Carolina Teachers College, later East Carolina College and still later East Carolina University, where he served for twenty-four years. He assumed responsibility for developing a graduate history program and served as adviser to students. His formidable teaching schedule included advanced courses in the histories of England, Russia, the Far East, European expansion, historiography, and his major field- American social and cultural history. By 1969, the year of his retirement, the Department had a well-defined and highly respected masters program in history thanks to Lawrence Brewster's direction.

During his lifetime Lawrence sought many ways to support the historical profession. His benefactions were extraordinary. He provided an endowment for East Carolina's History Department and financed annual graduate fellowships in history. In 1982, Arthur S. Link presented the first annual "Brewster Lecture" series. Lawrence provided subsidies to East Carolina College Publications in History and to the journal of he Association of Historians in North Carolina. His endowment to the Association of Historians in North Carolina was substantial. He endowed a professorship for East Carolina University historians with the explicit purpose of assisting research and publication.

Lawrence was affable, eager to hear the opinions of his colleagues, and proud to see the success of his endeavors. In 1974, the University dedicated the largest classroom quadrangle at East Carolina University in his honor.

Lawrence was a devoted Episcopalian. He often recalled his membership in the choir of Williamsburg's Bruton Parish Church. During his retirement he traveled extensively as historiographer of The Episcopal Diocese of East Carolina. His essay entitled "The Diocese of East Carolina, 1883-1963" appeared in The Episcopal Church in North Carolina, 1701-1959 (1987). His essay "Alfred Augustin Watson: Episcopal Clergyman of the New South" was published in volume three of East Carolina College Publications in History. His favorite recreation was frequent travel on Mississippi River steamboats. He was an active member of the Circle K Kiwanis chapter of Greenville and participated in the group's conventions.

After several years of declining health at the Cypress Glen retirement home of Greenville, Lawrence was admitted to Pitt Memorial hospital where he died on September 19, 1999. Before retirement he provided for the distribution of his estate in his last will and testament to the College of William and Mary, Duke University, and East Carolina University. Lawrence willed his home and real estate to St. Paul's Episcopal Church of Greenville. His endowments, the fulfillment of a generous and purposeful life, support historical and religious interests and constitute his legacy.