NAICS (North American Industry Classification System) and SIC (Standard Industry Classification) codes are an easy way to group companies engaged in the same economic activities.
SIC was used by the US and Canadian governments until 1987, when both countries adopted NAICS. Some commercial databases continue to use SIC, however.
You can search by NAICS and/or SIC in the following databases...
Research your industry, identify companies and trends with these resources...
Part of knowing researching your industry is also to understand your competitors. Here are some freely available resources that you may want to use for this: