Construction of the Beltway stalled in the 1960s as local resistance frustrated planners' attempts to turn other lines drawn on maps into reality. A number of planned freeways in Southeast Baltimore would have destroyed the closely-knit neighborhoods of Fells Point and Canton. The fierce battle that residents put up was eventually a successful one, cancelling the construction of numerous planned links and spurring the political career of Barbara Mikulski.
In the meantime, planners really wanted the rest of the Beltway to be finished, but that required the construction of an "Outer Harbor Crossing" across the Patapsco River estuary. Local railroads and shipping interests thought that bridges were bad for business, and pushed for a tunnel crossing similar to the Baltimore Harbor Tunnel (completed in 1953). But when the State finally started taking bids in the early 1970s, it became apparent that a bridge would be much cheaper to build. This decision was easily made, and construction of the final section of the Beltway began in the mid-1970's. The loop was finally completed when the Francis Scott Key Memorial Bridge opened in 1977.
As happened with most projects of this sort, construction of the Beltway created as many problems as it solved. It spurred development away from the city center and probably helped contribute to the rapid depopulation of the city in the decades that followed. Development rapidly absorbed the additional traffic capacity created, and along with the cancellation of other planned links, this allowed certain sections of the Beltway to back up with traffic every single day. On aggregate, however, traffic on the Baltimore Beltway is nowhere near as bad as the traffic on its counterpart to the southwest, the Capital Beltway. One hopes that no other traffic hells like that are ever spawned.
The Beltway has, however, succeeded in its goal of providing alternatives to driving through the city, as well as connecting Baltimore's suburbs. The Beltway can now be called "Baltimore County's Main Street" without anyone arguing over it.
Starting at the southern end of the Francis Scott Key Memorial Bridge, at the southern extreme of Baltimore, going clockwise:
Patapsco River (Francis Scott Key Memorial Bridge)
Exit 45, Glidden Road (closed, except for an Outer Loop on-ramp from Fort Armistead Road)
Exit 1, Quarantine Road (in to Curtis Bay; out Riviera Beach via Fort Smallwood Road)
Curtis Creek drawbridge (enter Anne Arundel County). From 1977 to 1983, there was a single two-lane drawbridge here. But a parallel drawbridge opened in 1983, allowing for four lanes of traffic on the western approach to the Key Bridge.
(Inner Loop) Exit 3a, Governor Ritchie Highway (MD 2) (in to Brooklyn, Federal Hill, and downtown; out to Glen Burnie, Severna Park, and Annapolis)
Exit 2, Arundel Expressway (MD 10) (out to Pasadena and Ritchie Highway)
(Outer loop) Exit 3a, Governor Ritchie Highway (MD 2)
Exit 3B, on-ramps from I-895 spur
Exit 4, Interstate 97 (out to BWI, Odenton, Annapolis, Bowie, Southern Maryland, Richmond and Norfolk)
Exit 5, Baltimore-Annapolis Boulevard (MD 648) (in to Pumphrey, Baltimore Highlands, and Westport; out to Linthicum, Ferndale, Glen Burnie)
Exit 6, Camp Meade Road (MD 170) (in to Pumphrey and Brooklyn; out to Linthicum and BWI)
Exit 7, Baltimore-Washington Parkway (MD 295) (in to Westport and downtown (Camden Yards); out to BWI, Fort Meade, Laurel, Greenbelt, and Washington, DC)
Upper Patapsco River (enter Baltimore County)
Inner Loop Exit 8, Nursery Road (in to Pumphrey; out to Hammonds Ferry Road and BWI)
Outer Loop Exit 8, Hammonds Ferry Road (in to Lansdowne, and Southwest Baltimore; out to Linthicum and BWI)
Exit 8A, Harbor Tunnel Thruway (Interstate 895) (in to the Baltimore Harbor Tunnel; out to I-95 South)
Exit 9, Hollins Ferry Road (in to Lansdowne)
Exit 10, Washington Boulevard (Alt US 1) (in to Southwest Baltimore and downtown (Camden Yards); out to Elkridge, Savage, Laurel, College Park, and Washington DC)
Exit 11, Interstate 95 (in to Downtown Baltimore and the Fort Mchenry Tunnel; out to Columbia, Savage, Laurel, the Capital Beltway, Washington DC, Richmond, and points south and east of the Appalachians)
Exit 12A, Southwestern Boulevard (US 1) (in to Wilkens Avenue; out to Halethorpe, Arbutus, and Washington Boulevard)
Exit 12, Wilkens Avenue (MD 372) (in to Southwest Baltimore; out to UMBC)
Exit 13, Frederick Road (MD 144) (in to Southwest Baltimore; out to Catonsville and Ellicott City)
Exit 14, Edmondson Avenue (in to Southwest Baltimore; out to Catonsville)
Exit 15, Baltimore National Pike (US 40) (in to Southwest Baltimore and downtown; out to Catonsville,
Ellicott City, and I-70)
Exit 16, Interstate 70 (out to Ellicott City, Mount Airy, Frederick, Hagerstown, and anywhere west of the Appalachian Mountains
Exit 17, Security Boulevard (in to Woodlawn; out to Security Square Mall)
Exit 18, Liberty Road (to Lochearn, Forest Park, West Baltimore, and Downtown, Randallstown, Eldersburg, and Frederick)
Exit 19, Interstate 795 (to Owings Mills, and Reisterstown, continuing on MD 140 to Westminster, Taneytown, and Gettysburg)
Exit 20, Reisterstown Road (MD 140) (in to Pikesville, Northwest Baltimore, and downtown, out to Owings Mills and Reisterstown)
Exit 21, Park Heights Avenue and Stevenson Road (in to Pikesville and Northwest Baltimore, out to Greenspring Valley)
Exit 22, Greenspring Avenue(in to Mount Wahington and Pimlico, out to Greenspring Valley)
Exit 23, Jones Falls Expressway (Interstate 83) (in to Mount Washington, Hampden, and Downtown Baltimore)
Exit 23, Falls Road (out to Greenspring Valley and Northwestern Baltimore County)
Exit 24, Baltimore-Harrisburg Expressway (out to Timonium, Cockeysville, Hunt Valley, northern Baltimore County, Shrewsbury, Pennsylvania, Stewartstown, York, and Harrisburg, Central and Northern Pennsylvania, and western New York)
Exit 25, Charles Street (in to Towson, Govans, Guilford, Charles Village, Johns Hopkins University, Charles Village, and downtown; out to Lutherville)
Exit 26, York Road (in to Towson, Govans,and Waverly; out to Lutherville, Timonium, Cockeysville, Northenr Baltimore County, and York PA)
Exit 27, Dulaney Valley Road (in to Towson; out to Loch Raven and northeast Baltimore Couunty)
Exit 28, Providence Road (in to Towson; out to Loch Raven)
Exit 29, Loch Raven Boulevard (MD 542) (in to Hillendale and North Baltimore; out to Cromwell Bridge Road, which goes to Loch Raven)
Exit 30, Perring Parkway (MD 41) (in to Parkville, North Baltimore, Morgan State University, Montebello and Harford Road; out to Carney)
Exit 31A-B, Harford Road (MD 147) (in to Parkville, Northeast Baltimore (Hamilton) , and downtown; out to Carney, Fallston, and Bel Air)
Exit 31C, Whitemarsh Boulevard (MD 43) (out to Whitemarsh, I-95, being extended to Middle River) opened in the mid-1990s.
Exit 32, Belair Road (US 1) (in to Fullerton, Overlea, Northeast Baltimore (Gardenville); out to Perry Hall, Fallston, Bel Air, Conowingo, and Philadelphia)
Exit 33, John F. Kennedy Memorial Highway (I-95) (in to Southeast Baltimore (Canton), the Fort McHenry Tunnel the Harbor Tunnel, downtown; out to Whitemarsh, Edgewood, Aberdeen, Havre de Grace, Elkton, Wilmington, Philadelphia, the New Jersey Turnpike and anywhere in the Northeast)
Exit 34, Phildelphia Road (MD 7) (in to Rosedale and Pulaski Highway; out to Rossville, Whitemarsh, Edgewood, Aberdeen)
Exit 35, Pulaski Highway (US 40) (in to southeast Baltimore (Highlandtown) and downtown; out to Middle River, Joppatowne, Edgewood, Abingdon, Aberdeen, Havre de Grace, Elkton, and Wilmington)
Things get a little complicated past this point, because of the way the Beltway was constructed. From 1962 to 1972, the freeway ended a few hundred yards southeast of the Pulaski Highway interchange, dumping traffic onto Race Road, a small road which allowed traffic to access the Essex/Middle River/Back River Neck area. In 1972 the freeway was extended into Essex itself, dumping traffic onto Old Eastern Avenue. Although this looked like a continuous extension of the Beltway, it wasn't. It was really the first section of the
(Exit 36) Southeast Freeway (MD 702) (out to Essex) just past the closed interchange with Race Road (which still passes under the Belway, connecting into an industrial park). You actually take this "exit" if you go straight ahead. The Southeast Freeway was originally intended to be extended down through Back River Neck to become the eastern approach to a northern Chesapeake Bay Crossing. For about 15 years it ended at Old Eastern Avenue. It was extended 3 more miles in the 1990s as a four-lane surface road down into Back River Neck, increasing development pressure in one of the last rural areas close to Baltimore.
To stay on the "Beltway" you bear to the southwest at Exit 36, onto a section of one of the disputed freeways. When the Francis Scott Key Bridge project went forward in 1974, a half-mile section of the Windlass Freeway (intended to be an extension of Moravia Road northeast into Essex and Middle River) was built to help connect up the Beltway.
There is no Exit 37. After a half mile on the "Windlass Freeway", the Belway makes a sudden 90-degree bend to the southeast, onto a section of the "Patapsco Freeway" that was built for the same purpose. A numeric placeholder was left in case the connector to Moravia Road was ever built.
But it's clear now that other sections of these freeways will never be built, and so neither will the interchange between the two. Tractor-trailers often find it difficult to negotiate this bend, making it one of the most dangerous locations for accidents around Baltimore.
Back River, or rather the marshes at its head.
Exit 38, Eastern Boulevard (MD 150)(in to Eastpoint, Highlandtown, Fells Point, and downtown; out to Essex, Middle River, and Chase)
Exit 39, Merritt Boulevard (in to Dundalk)
Exit 40, North Point Boulevard (MD 151) (in to Eastpoint and East Baltimore; out to parallel Beltway)
Exit 41, Cove Road (to North Point Boulevard and Dundalk)
Exit 42, North Point Boulevard (out to Edgemere and Sparrows Point)
From 1977 until 2000, the Beltway past this point existed as a two-lane viaduct skirting the north side of Bethlehem Steel's immense Sparrows Point complex. This was extremely dangerous stretch of road, as there was nowhere for anyone to go if someone accidentally crossed the line. Traffic was constricted enough to keep the southeast side of the Beltway underutilized.
Exit 43, Peninsula Expressway (MD 158) (in to Dundalk, out to Bethlehem Steel)
Bear Creek. In the late 1990's, traffic on the west side had become so bad that improving the eastern approach to the Key Bridge became a necessity. A parallel Bear Creek Bridge was built, the viaduct was demolished, and a four-lane surface road was constructed north of Sparrows Point. The Beltway now has at least four lanes of traffic all the way around.
Exit 44, Broening Highway (in to Dundalk and Canton)
Patapsco River (Francis Scott Key Memorial Bridge) (enter Baltimore City, completing the loop)
Experience with the damn thing would probably have provided enough information for a decent writeup, but I consulted various maps and other sources, including:
Location Studies: Chesapeake Bay Crossings. State Roads Commission of Maryland, J. E. Greiner & Co., January 1964