The 1891 Keller's Mill Covered Bridge is a covered bridge that spans Cocalico Creek in Ephrata Township, Lancaster County, Pennsylvania. Lancaster County has the most covered bridges per county in Pennsylvania with 29 covered bridges.

A county-owned and maintained bridge, its official designation is the Cocalico No. 5 Bridge. It is also sometimes known as Guy Bard Covered Bridge (after a local jurist) and Rettew's Covered Bridge (after the person that whom Rettew's Road is named).

Due to heavy road traffic on the aging, one-lane bridge, the construction of a new steel and concrete bridge to bypass the covered bridge occurred in the summer of 2006. According to Ephrata Township supervisor Clark Stauffer, the bridge has been disassembled and will be reassembled a few miles downstream to replace an existing one-lane Mill Creek Road bridge.

Keller's Mill Covered Bridge was originally built by Elias McMellen in 1873 at a cost of US$2,075. After being swept away in flooding, the bridge was rebuilt in 1891, again by McMellen. It stayed there until it was disassembled and moved in 2006. The bridge was reconstructed in 2009. The bridge was reopened on Middle Creek Road in December 2010.

Keller's Mill Covered Bridge has a single-span, wooden, double Burr arch trusses design with the addition of steel hanger rods. The deck is made from oak planks. The bridge is the only all-white bridge in the county, the only bridge to have survived the transition from whitewashing to the red color commonly used in barns throughout the county. The bridge is not painted on the inside. Its length was a 62 feet span with a 74 feet total length. Its width was 13 feet 2 inches clear deck and 15 feet total width, with an overhead clearance of 11 feet. It had an under clearance of 9 feet 8 inches.

After being rebuilt in 2010, its length is a 72 feet span and a 74 feet total length. Its width is 13 feet 2 inches clear deck and 16 feet total width, with an overhead clearance of 9 feet 6 inches and an under clearance of 13 feet 8 inches.

Of the 1,500 covered bridges that once stood in the state of Pennsylvania, as of 2019, approximately 200 remain.

Posted to the National Register of Historic Places on December 10, 1980.

Located at:  N40 09.851    W76 13.949     -     WGCB #38-36-13

Photographed in July of 2019.