Big River Crossing (Harahan & Frisco Bridges)

You watch from a boardwalk laid on the former north automobile deck of the Harahan Bridge, so the Union Pacific tracks are at your own eye level and immediately beside you rather than below or above. Measured on OpenStreetMap way geometry, the nearer of the Harahan's two track centrelines sits approximately 7 metres (23 feet) from the boardwalk centreline and the farther one approximately 13 metres (44 feet); a railfan blog describing the same vantage point puts trains "about 10 or 15 feet from anyone on the walkway, on the other side of a metal grill". HistoricBridges.org confirms the barrier is substantial fencing, and that the original riveted lattice railings of the 1917 wagonway were left in place when the deck was converted, so you are shooting past two layers of ironwork.

The second half of the interest is 200 feet (61 metres) to the south, where BNSF's single track crosses the 1892 Frisco Bridge. Because the two structures are parallel and the Harahan's piers were deliberately built directly upstream of the Frisco's to keep the navigation channels clear, a BNSF train is seen through and past the Harahan's own steelwork rather than in the open; the trusses cut across the frame unless the shot is timed to the gaps between verticals.

The crossing is nearly a mile long, so a train that appears at one abutment takes time to reach you, and there is nowhere to retreat to: the deck is open along its whole length. Approach warning is limited to sound and to watching the far portal. One useful tell after dark is the lighting itself, which Encyclopedia of Arkansas records is switched off for rail and barge crossings, a condition attached to the system when it was installed. The bridge going dark is the cue that something is coming, and it is also why a lit bridge and a moving train cannot appear in the same photograph.

The vantage point is 108 feet (33 metres) above the water, the clearance Wikipedia gives beneath the Harahan's main span, and that span is 791 feet (241 metres) of steel over the main navigation channel on the Memphis side. The deck is a linear world: 4,973 feet (1,516 metres) of bridge in total, of which 2,550 feet (777 metres) runs from the east anchorage on the Memphis bluffs to Pier 5 on the Arkansas flood plain, with a further 2,363 feet (720 metres) of tower-and-girder viaduct out to the west abutment.

Looking northeast, the downtown Memphis skyline stands above the bluff, with the Hernando de Soto Bridge carrying Interstate 40 across the river approximately 2.8 km (1.7 mi) upstream. Looking southwest, past the Union Pacific tracks, the Frisco Bridge's 790-foot (241-metre) main span and its two 600-foot (183-metre) flanking spans sit 65 feet (20 metres) above the water, lower and visibly older; beyond it the 1949 Memphis & Arkansas Bridge carries Interstate 55. HistoricBridges.org notes this is three historic cantilever trusses side by side and states there is no other such trio anywhere in North America.

Below, towboats push barge strings through commercial working water rather than scenery; the Arkansas bank is flat flood plain rather than built up, so the western half of the walk is river, willows and sky. Underfoot the surface changes: OpenStreetMap records one boardwalk segment as paved and another as metal, and the grating section transmits both bridge vibration and the sound of a passing train through your feet. Wind funnels along the deck with nothing to break it for nearly a mile in either direction.

This is the site of the first railway crossing of the Mississippi below St. Louis. Work on what was then called the Memphis Bridge began in 1888 for the Kansas City, Fort Scott and Memphis Railway and finished on 12 May 1892. The Tennessee Encyclopedia records it as the third-longest bridge in the world when it opened, and says it was renamed the Frisco in 1903 when the St. Louis and San Francisco Railway bought it. Its chief engineer was George S. Morison, it was built entirely of then-new open-hearth steel, and it was named a National Historic Civil Engineering Landmark in 1987. It is a BNSF Railway bridge today; the Frisco name is history, not the operator.

The Harahan followed because one track was not enough. Memphis mayor E. H. Crump met Rock Island officials on 5 February 1912, the Iron Mountain and the Cotton Belt joined, and a joint bridge and terminal company was formed. Congressman Kenneth McKellar threatened to block the federal permit unless road lanes were included, and in August 1912 the Rock Island agreed to a 4-million-dollar bridge carrying wagonways. Ralph Modjeski was instructed to prepare plans on 10 April 1913. The first train crossed on 14 July 1916, with the planned celebration cancelled because of the war in Europe; the wagonways did not open until 17 September 1917, delayed by trouble with a wooden viaduct in Arkansas. It is a Union Pacific bridge today, not a Rock Island one.

Those wooden wagon decks were a liability, because locomotive sparks reached plank surfaces. Fire heavily damaged the bridge in September 1928 and destroyed the eastbound wood-plank roadway; sources disagree on the day, with the Tennessee Encyclopedia giving 18 September 1928 and Mike Condren's pages 28 September 1928. Road traffic ended when the Memphis & Arkansas Bridge opened 1949, and the north deck then stood unused until 2016.

A railway company letting the public walk the length of one of its live main-line river bridges is close to unheard of, and HistoricBridges.org says so plainly: the walkway is unusual both for its size and because it is rare for a railroad to permit a public path on one of its bridges. Big River Crossing opened on 22 October 2016; its operator describes it as the longest public pedestrian and cyclist bridge across the Mississippi at nearly a mile long, and HistoricBridges.org calls it the country's longest active rail, bicycle and pedestrian bridge. Union Pacific 844 crossed the Harahan under steam the morning it opened.

The second distinction is the pairing. From one standing position you can see work by two of the outstanding American bridge engineers of consecutive centuries: George S. Morison's 1892 Frisco Bridge and Ralph Modjeski's 1916 Harahan, parallel and 200 feet (61 metres) apart, with the 1949 Memphis & Arkansas highway bridge beyond. HistoricBridges.org states that this trio of historic cantilever trusses has no equivalent anywhere in North America. You are not comparing two eras from photographs; you are comparing the structures against each other in one frame, from a deck attached to one of them.

The third is preserved detail within arm's reach. The 2016 conversion kept the original riveted lattice railings of the 1917 vehicular deck rather than stripping them, so the walkway still reads as a road. The Arkansas approach retains the old wagonway road stubs pointing toward Interstate 55, near 35.135142, -90.085369. And the crossing carries public access across a state line, from Main Street in Memphis, Tennessee to Broadway in West Memphis, Arkansas, on a structure whose piers were set directly upstream of the Frisco's so that both bridges could share the same navigation channels.