The Maryland flag has been described as the perfect state flag, with bold colors, interesting patterns, and correct heraldry—a flag that fairly shouts "Maryland." The design of the flag comes from the shield in the coat of arms of the Calvert family, the colonial proprietors of Maryland. George Calvert, first Lord Baltimore, adopted a coat of arms that included a shield with alternating quadrants featuring the yellow and black colors of his paternal family and the red and white colors of his maternal family, the Crosslands. When the General Assembly adopted a banner of this design as the state flag, a link was forged between modern-day Maryland and the very earliest chapter of the proprietorship of the Calvert family.

Despite the antiquity of its design, the Maryland flag is of post-Civil War origin. Throughout the colonial period, only the yellow and black Calvert family colors were mentioned in descriptions of the Maryland flag. After independence, the use of the Calvert family colors was discontinued. Various banners were used to represent the state, although none was adopted officially as a state flag. By the Civil War, the most common Maryland flag design probably consisted of the great seal of the state on a blue background. These blue banners were flown at least until the late 1890s.

The Calvert family coat of arms was reintroduced in Maryland in an 1854 law that called for a new great seal based on the Calvert design. The seal created pursuant to this act contained several inaccuracies, and in 1876, the General Assembly provided for a new great seal that conformed closely to the Calvert original. Reintroduction of the Calvert coat of arms on the great seal of the state was followed by a reappearance at public events of banners in the yellow and black Calvert family colors. Called the "Maryland colors" or "Baltimore colors," these yellow and black banners lacked official sanction from the General Assembly but appear to have quickly become popular with the public as a unique and readily identifiable symbol of Maryland and its long history.

The red and white Crossland arms gained popularity in quite a different way. Probably because the yellow and black "Maryland colors" were popularly identified with a state that, reluctantly or not, remained in the Union, Marylanders who sympathized with the South adopted the red and white of the Crossland arms as their colors. Following Lincoln's election in 1861, red and white "secession colors" appeared on everything from yarn stockings and cravats to children's clothing. Federal authorities vigorously prosecuted people who displayed these red and white symbols of opposition to the Union and to Lincoln's policies.

During the war, Maryland-born Confederate soldiers used both the red and white colors and the cross-botonee design from the Crossland quadrants of the Calvert coat of arms as a unique way of identifying their place of birth. Pins in the cross-botonee shape were worn on uniforms, and the headquarters flag of the Maryland-born Confederate general Bradley T. Johnson was a red cross-botonee on a white field.

By the end of the Civil War, therefore, both the yellow and black Calvert arms and the red and white colors and botonee cross design of the Crossland arms were clearly identified with Maryland, although they represented opposing sides in the conflict. As officers and soldiers returned home after the war to resume their peacetime occupations, the greatest challenge facing the country was reconciliation. Nowhere was the problem more serious than in deeply divided Maryland, where veterans who had fought under the red and white secession colors" had to be reintegrated into a state that had remained true to the Union.

As the slow process of reconciliation took place in post-Civil War Maryland, a new symbol emerged. A flag incorporating alternating quadrants of the Calvert and Crossland colors began appearing at public events. While the design derived directly from the seventeenth-century Calvert family coat of arms, for Marylanders of the 1880s, the new banner must have conveyed a powerful message. The passage of time had gradually diminished the passions of former Rebels and Yankees, permitting them to work together once again. Now the colors they had fought under had come together as well, symbolically representing through this new flag the reunion of all the state's citizens.

Neither the designer nor the date of origin of this new Maryland flag is certain, but a banner in this form was known at least by October 1880. Flags incorporating four quadrants alternating between the yellow and black Calvert arms and the red and white Crossland arms appear in published sketches by Frank B. Mayer depicting the huge 150th birthday parade held in Baltimore that month. At the dedication ceremonies for the Maryland monument at the Gettysburg Battlefield eight years later, in October 1888, Maryland National Guard soldiers escorting Governor Elihu E. Jackson carried a sizable flag with the alternating Calvert and Crossland colors. A year later, in October 1889, the Fifth Regiment, Maryland National Guard, adopted a flag in this form as its regimental color. The Fifth Regiment thereby became the first organization to officially adopt what is today the Maryland flag.

The adoption of this new flag by the Fifth Regiment helped popularize the design. The Fifth was the largest component of Maryland's military after 1870, and it played a conspicuous part in major public events both in and out of the state. Organized in May 1867, the Fifth Regiment was the successor organization to the Old Maryland Guard, a military unit formed in Baltimore in 1859 that dissolved when most of its officers and men went south in 1861 to join the Confederate Army.

True to its heritage, the original Fifth Regiment consisted primarily of Maryland-born former Confederate officers and soldiers. The new regimental color adopted in 1889, combining the traditional yellow and black "Maryland colors" with the red and white "secession colors" in the form of a botonee cross, must have seemed especially appropriate to members of the Fifth. The colors symbolically represented what had happened to the Fifth Regiment itself in the quarter century since the Civil War. Originally denounced as a "Rebel Brigade," the Fifth had by the 1870s become Maryland's premier military organization, attracting Union veterans as well as former Confederates. From its inception, the Fifth Regiment had demonstrated through its prominent participation in public events and with its summer encampments in the north that former Confederates could be good soldiers and loyal citizens of the state and the nation.

The Fifth Regiment's new regimental color was not the only example of former Confederates perpetuating and thereby popularizing the use of the red and white Crossland colors and the cross-botonee design. The monument on Culps' Hill at the Gettysburg Battlefield commemorating the Second Maryland Infantry, CSA, carries a cross botonee on each face, and the Maryland Line Confederate Soldiers' Home, established in Pikesville in 1888, featured a large cross botonee over the main gate. Confederate veterans' organizations used the cross-button on service badges and on invitations to events they sponsored. By 1905, the Fifth Regiment had switched out the silver eagle on the flagstaff bearing its regimental color for a cross-botonee, starting a tradition that would later become a legal requirement.

In 1904, the General Assembly affirmed the popular support shown for a banner composed of alternating Calvert and Crossland quadrants by declaring it the state flag. In 1945, a gold cross botonee was made the official ornament for a flagstaff carrying the Maryland flag.

The Maryland flag, shown on a staff properly ornamented with a gold cross botonee, is therefore much more than a symbol of state sovereignty. The flag excels as a state banner because it commemorates the vision of the founders while reminding us of the struggle to preserve the Union. It is a unique symbol of challenges met and loyalties restored, a flag of unity and reconciliation for all the state's citizens.