The Dominion Atlantic Railway was created on October 1, 1894, through a merger of two other systems, the Windsor and Annapolis Railway (W&A) and the Western Counties Railway (WCR). The W&A ran southwest from Windsor to Annapolis Royal, while the WCR ran northeast from Yarmouth to Digby. This left a gap in rail service between Digby and Annapolis Royal which was filled in July of 1891, with a little financial assistance from the government. On January 1, 1912, the D.A.R. was formally leased to the Canadian Pacific Railway (CPR) for 999 years.
This bridge is on that section of trackage, so was most certainly built at that time. The bridge is just south of Annapolis Royal spanning a small river (whose name escapes us). By the 1980s, with passenger service still in operation, the bridges along most of the line from Yarmouth to Kentville were reaching the end of their service life at the same time that passenger traffic was rapidly diminishing. As a result, on March 27, 1990, the CPR abandoned the DAR's trackage west of Kentville to Yarmouth, and this bridge along with it.
The bridge consists of a very light (for a railway bridge) through truss centre section with steel girder approaches on each end. In total it is about 600 feet in length, with the truss section being about 175 feet long.
A great photo set of the DAR, its engines, bridges, stations, etc. can be seen
HERE