Upon the resignation of Rev. Whitlock, God led the church to call Rev. J. A. Sullivan of Washington, NC. Dr. Sullivan accepted God's call and became the Pastor on December 5, 1911, which marked the beginning of 27 years of phenomenal growth and outreach for the church.

During the early Sullivan years, numerous people utilized their talent by doing significant work for the Glory of God and to strengthen the work of God in the Church. Under the spirit-filled leadership of Brother Sullivan, and with his emphasis on evangelism, the church membership and the Sunday School enrollment continued to grow. In early 1916, in order to provide additional Sunday School space, the church purchased the "B.C. Moore" Drug Company located on the South side of the church. This site later became the parsonage, and the property at 717 North 5th Street was sold.

It was during these years, perhaps mid-1916, that the church's name was changed to Calvary Baptist Church, although no record is found in the minutes.

In 1917, during the World War I era, Rev. Sullivan recommended that the church secure some vacant lots on which to raise vegetables, due to the threatened food shortage. He also recommended that the store, which was owned by the church, be equipped for a community cannery. The Church set aside fifty dollars to assist those who desired to make gardens. During these difficult years, church members also assisted with cutting wood for those unable to buy fuel. It was not unusual to see Brother Sullivan or one of his Deacons hauling wood in a trailer pulled by the Pastor's car.

On December 31, 1919, the church held its 25th anniversary celebration during watch night services. Brother J. W. Hollis was appointed as Assistant to the Pastor on March 24, 1920, for the specific purpose of looking after pledges and purchasing materials during the renovation project. The Calvary building Corporation was organized to oversee the project. Improvements included adding brick veneer to the old framed building, a new Sunday School annex, a new two-story classroom building and a new large, well arranged and convenient pastorium. When the buildings were completed in August, 1922, Brother J. W. Hollis resigned from his position as Assistant to the Pastor. The total cost of all improvements was $55,000. However, the Helping Hand Sunday School Class installed new carpet in the church sanctuary and linoleum in the vestibules at an additional cost of $960.

The church's outreach expanded significantly in 1928 when Rev. Sullivan, in association with Mr. R. A. Dunlea, was instrumental in bringing Wilmington's first radio station, "W.R.B.T.", into existence. The station that went on the air June 19, 1928, was the vehicle for many hours of gospel radio programs, reaching thousands throughout the area.

Rev. Sullivan and the church received national recognition for the soul-winning method, "Won by One", developed by Rev. Sullivan. "Won-by-One" was adopted by the Sunday School Board of the Southern Baptist Convention and was used throughout the denomination to win souls to Christ. During Mr. Sullivan's dynamic pastorate, eight men answered God's call into the gospel ministry and were ordained by the church. They were: E. E. Bryant (1918), J. E. Allard (1921), W. S. Strickland (1924), T. H. Williams (1926), C. P. Herring (1930), E. W. Pate (1934), G. W. Bullard (1937), L. R. Jordan (1937), and Dennis Larkins (date unknown).

In April 1936, the church celebrated its 50th anniversary with a special ceremony and a reading of the church's history compiled by Mrs. S. F. Garrison. Generous gifts to the church were acknowledged such as a communion service presented by Mrs. S. L. Smith in memory of her husband. During the anniversary celebration the following poem was read:

God bless our church and those who love it,
Fair be the skies above it.
Grant that these friends from year to year
Shall build their happiest memories here.
-Anonymous

Due to failing health, Rev. J. A. Sullivan retired on January 1, 1938. During his 27 year-long ministry, membership in the church swelled to 1,350 and, at the same time, Calvary Baptist Church became an important beacon of light in the community. With its emphasis on evangelism, Calvary Baptist Church stood for the best interests of the community and could always be counted to take its share of responsibility, both civic and religious.