Optimal Postgres text index for LIKE query?

Using Postgres 9.5, I have a table addresses.

CREATE TABLE addresses (
    id        integer PRIMARY KEY,
    address   text
);

In that table I have 7.5 million rows. Example:

1, "1600 Pennsylvania Avenue NW, Washington, DC, 20500"

I'm using this table for an autosuggest search in my application so I need to use this type of query:

SELECT * FROM addresses WHERE address LIKE '123 Main St%';

I created this index:

CREATE INDEX address_idx ON addresses (address);

But the problem is it's taking around 1 sec which is too slow.

Here's the query plan:

EXPLAIN SELECT * FROM addresses WHERE address LIKE '123 Main St%';
----
Seq Scan on addresses  (cost=0.00..161309.76 rows=740 width=41)
  Filter: (address ~~ '123 Main St%'::text)

I tried creating a few types of gin indexes but they either had no effect or made the query slower. I'm not sure if I was using them correctly though.

Any ideas on how to create an index that's optimized for this kind of query?

EDIT

The best solution found so far is to use a text range scan:

SELECT *
FROM addresses
WHERE address >= '123 Main St' AND
      address <= concat('123 Main St', 'z');