The launch facilities at Cape Canaveral, FL are located at a latitude of about 28.5° N, so that puts a hard lower bound on inclinations from that site. I assume there are well-defined azimuth limits for launches from the Cape, but what is the highest inclination mission that has actually launched from here? If it was high enough, was it visible along the East coast of the U.S.?
Due to range safety requirements, which preclude launch trajectories that fly over populated areas, the maximum inclination by a standard launch from CCAFS/KSC is approximately 57 degrees. There was one mission, however, that exceeded that. STS-36, a classified shuttle mission, was launched to an inclination of 62 degrees, through the use of a "dog-leg" maneuver after SRB separation. This did result in an overflight of portions of eastern Canada, but this occurred at a sufficient altitude and velocity not to endanger the overflown region. This maneuver, in which the vehicle turned significantly northward after staging, came at a steep performance penalty, however.
To revisit this question, it does appear that the during the 1950s & 1960s, a number of extreme inclination and polar launches did indeed take place from Cape Canaveral in Florida.
The range safety limitations placed on launches from Florida was only enacted after a number of polar launches had already taken a place (possibly for good reason at the time too, as it is reported a 1960 Thor launch killed a cow in Cuba).
The launch of ESSA9 onboard a Delta 1E rocket from LC-17B at Cape Canaveral
The most extreme of these being ESSA9 (1969-016A), a 145kg meteorological satellite which launched on 26 February, 1969 on a Delta E1 launch vehicle from Cape Canaveral LC-17B, with the orbital parameters of:
- Periapsis: 1427km
- Apoapsis: 1508km
- Inclination: 101.79°
This inclination actually exceeds a typical polar orbit, and is technically a very weak retrograde orbit.
Based on this document the maximum inclination possible is 37 degrees (from north) and the minimum is 114 degrees (from north).
I don't know if how close any mission got to the limits, but most polar launches occur from Vandenberg