I-77 carries three lanes from the South Carolina line to downtown Charlotte, and four lanes from downtown Charlotte north to I-85. The interchange with I-485, exit 2, is the only 4-level "stack" interchange in the state. 

I-77 intersects I-277 at exits 9 and 11. Exit 9 is a standard cloverleaf with C/D lanes on 77; exit 11 is a rather complicated 3-level interchange. 

The interchange with I-85, exit 13, is interesting in that the lanes of I-77 cross over each other and back, so that where 77 passes over 85 the lanes are each on the "wrong" side (Image #1). This arrangement conserves space and concrete at the expense of using left-side entrances and tight ramps. This interchange ended up being quite different from its original design (Image #2), which would have featured a left-lane weave area on northbound 77. 

The interchanges with I-40 (exit 51) and U.S. 421 (exit 73) are simple cloverleaves. 

Exit 83, near Elkin, is a partial interchange with U.S. 21: a left exit for northbound traffic, and a right-hand entrance onto I-77 south. There's no southbound exit or northbound entrance here. 

Exit 101, for I-74 (photo at top), is a "Directional T" or "split" interchange.  From southbound I-77, this is a left-hand exit and entrance; from northbound 77, it's a right-hand exit and entrance. 
 

The '62 RMcN atlas (Image #3) shows 77 tentatively running west of its current alignment near the Virginia line, close to where N.C. 89 enters Virginia. This would have put 77's hillclimb portion would mostly in N.C., rather than entirely in Virginia, as would be the ultimate alignment. 

Construction of 77 got underway in the mid-1960s. The first stretches of 77 to open were those east of Statesville (exits 42-54) and Elkin (exits 79-83), in late 1965 (see Image #4). Around 1968, 77 opened between exits 28 and 33 in the Cornelius/Davidson area. 

By 1973, gaps north of the Charlotte area were filled in, so that 77 was opened from N.C. 73 (exit 28) all the way to exit 73 north of Elkin. The highway from Cornelius south to Charlotte was opened in 1975. Finally, around 1978, I-77 north from exit 73 to the Virginia border became the last segment of 77 to be opened in the state. 

I-77 through Charlotte: The North-South Expressway. Interstate 77 was planned to end at I-85, but talk of extending 77 further south started soon after construction of the Interstate system got underway. 

A 1960 long-range plan for Charlotte's roads called for building something called the North-South Expressway, which "would extend from Interstate Route 85 Expressway through the central area of the city to a point near the... state line west of Pineville"[1]. The 1960 plan did not number the North-South Expressway as part of I-77, but the preliminary design routed it almost exactly along modern 77, exit for exit. 

The North-South Expressway was to end short of the South Carolina line -- this road was Charlotte's idea, not yet part of any federal plan. The approximate cost of the 9.3-mile (this seems a couple miles low) road was pegged at $20.2 million. Construction was to take place in three segments: near downtown Charlotte in the late 1960s, north to I-85 in the early 1970s (including the original interchange with I-85 shown above) and south to the state line in the late 1970s. The plan called for the expressway to open completely by 1980. 

The state beat that date by about five years. By 1966, construction of the expressway began near the S.C. border and progressed north. In 1967, the Federal government approved several extensions to the Interstate system, and I-77 south to Columbia was almost certainly one of them. With new Federal funding, construction of the expressway would be accelerated, although with its official assimilation into I-77 the N-S Expressway name disappeared. 

By 1968, I-77 was open from the state line north to Woodlawn Road (exit 6). By 1973 it was completed further north, to the Brookshire (nee Northwest) freeway (exit 11). By 1975, the highway was completely finished through I-85 and north to Statesville. 

Upgrades. Before the mid-1990s, 77 had carried six lanes only near downtown Charlotte, and four everywhere else. Widening to six lanes through most of southern Charlotte started in 1989 and finished in 1993. Unlike the I-85 widenings that were also going on at the time, no overpasses were relocated or replaced during the widening. Instead, 77's original grassy median was filled in with an extra lane in each direction. But now three lanes each way aren't even enough; see below. 

In the mid-1990s, a fourth lane in each direction was added to 77 through downtown Charlotte. 

The Sam Furr Road interchange (exit 25) opened in July 1992. The Charlotte Observer Web site contains a series on the rapid growth of the Exit 25 area. 

The I-485 interchange (exit 2) started construction in 1992. It was opened to eastbound 485 in October 1994 and completely in 1996. I-77 now opens up to four lanes in each direction through here. 

The I-74 (former N.C. 752) interchange opened in early 1994. I-77 was built to accommodate this interchange back in the 1970s: the spread median widens here, and the northbound lanes are on naturally higher ground than the southbound lanes are, allowing for easy construction of an underpass. (No, the idea behind I-74 doesn't date from the 1970s. But the state saw the need to connect 77 with the U.S. 52 freeway southeast to Winston-Salem early.)

The Tyvola Road interchange (exit 5) was upgraded from a simple diamond to a SPUI in the fall of 1998. 
 

Northern Mecklenburg. North of Charlotte, the northern Meck/southern Iredell area has become increasingly popular as a permanent-residence communitym thanks to lower Iredell taxes and the presence of Lake Norman. The large number of commuters from this area into Charlotte has caused long rush-hour delays on 77 north of Charlotte. 

Widening of I-77 from I-85 north to N.C. 73 (exit 28) is a matter of when, not if. The state has moved dates around, first later due to inadequate funding, then sooner due to motorist complaints and litigation delaying other projects elsewhere in the state. As of February 2001 some work should start by the spring of 2002. 

From I-85 north to the future I-485 interchange, I-77 will carry eight lanes. The state is attempting to start widening work by early 2002; if this happens it should finish within a couple of years. The city of Charlotte has requested the state look into building reversible carpool lanes, where one lane of the freeway would switch direction during rush hour. This would require building moveable barriers, or a separate roadway with reversible lanes, and almost certainly increase the cost of the widening. [2] 

From the future 485 north to N.C. 73, I-77 be widened to six lanes. [2] Construction will not start until after 2008. 

The entire widening project, I-3311, runs 12.0 miles and costs $100 million. [3]
 

If and when I-74 is completed, the northernmost 2-3 miles of 77 in N.C. will be multiplexed with it. 

I-77 is signed for Charlotte as far away as the 81/77 multiplex in Wytheville, Virginia -- 143 miles away, according to signs in Wytheville. 

I-77 likes cities beginning with C: Columbia, Charlotte, Charleston, Cambridge (Ohio), Canton and Cleveland.